[Federal Register Volume 78, Number 192 (Thursday, October 3, 2013)]
[Proposed Rules]
[Pages 61621-61666]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-23725]
[[Page 61621]]
Vol. 78
Thursday,
No. 192
October 3, 2013
Part V
Department of the Interior
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Fish and Wildlife Service
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50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Proposed Threatened
Status for the Western Distinct Population Segment of the Yellow-billed
Cuckoo (Coccyzus americanus); Proposed Rule
Federal Register / Vol. 78 , No. 192 / Thursday, October 3, 2013 /
Proposed Rules
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[FWS-R8-ES-2013-0104; 4500030113]
RIN 1018-AY53
Endangered and Threatened Wildlife and Plants; Proposed
Threatened Status for the Western Distinct Population Segment of the
Yellow-billed Cuckoo (Coccyzus americanus)
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Proposed rule.
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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to
list the yellow-billed cuckoo in the western portions of the United
States, Canada, and Mexico (western yellow-billed cuckoo) as a
threatened distinct vertebrate population segment under the Endangered
Species Act of 1973, as amended (Act). If we finalize this rule as
proposed, it would extend the Act's protections to the western yellow-
billed cuckoo. The effect of this regulation would be to add the
western yellow-billed cuckoo to the List of Endangered and Threatened
Wildlife under the Act.
DATES: We will accept comments received or postmarked on or before
December 2, 2013. Comments submitted electronically using the Federal
eRulemaking Portal (see ADDRESSES section, below) must be received by
11:59 p.m. Eastern Time on the closing date. We must receive requests
for public hearings, in writing, at the address shown in the ADDRESSES
section by November 18, 2013.
ADDRESSES: You may submit comments by one of the following methods:
(1) Electronically: Go to the Federal eRulemaking Portal: http://www.regulations.gov. In the Search box, enter FWS-R8-ES-2013-0104,
which is the docket number for this rulemaking. You may submit a
comment by clicking on ``Comment Now!''
(2) By hard copy: Submit by U.S. mail or hand-delivery to: Public
Comments Processing, Attn: Docket No. FWS-R8-ES-2013-0104; Division of
Policy and Directives Management; U.S. Fish and Wildlife Service; 4401
N. Fairfax Drive, MS 2042-PDM; Arlington, VA 22203.
We request that you send comments only by the methods described
above. We will post all comments on http://www.regulations.gov. This
generally means that we will post any personal information you provide
us (see the Information Requested section below for more information).
FOR FURTHER INFORMATION CONTACT: Jennifer Norris, Field Supervisor,
U.S. Fish and Wildlife Service, Sacramento Fish and Wildlife Office,
2800 Cottage Way, Room W-2605, Sacramento, California 95825, by
telephone 916-414-6600 or by facsimile 916-414-6712. Persons who use a
telecommunications device for the deaf (TDD) may call the Federal
Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Executive Summary
Why we need to publish a rule? Under the Act, if a species is
determined to be an endangered or threatened species throughout all or
a significant portion of its range, we are required to promptly publish
a proposal in the Federal Register and make a determination on our
proposal within 1 year. Listing a species as an endangered or
threatened species can only be completed by issuing a rule.
This rule proposes the listing of the yellow-billed cuckoo as a
threatened species in western North America as a distinct vertebrate
population segment (DPS) under the Act and our policy regarding the
recognition of DPSs (61 FR 4721; February 7, 1996).
What does this rule consist of and what is the potential outcome of
this rule making? This document consists of a proposed rule to list
populations of the yellow-billed cuckoo in the western United States,
Canada, and Mexico as a threatened species. This rule, if finalized,
will add the western yellow-billed cuckoo to the list of endangered or
threatened species.
What is the basis for our action? Under the Act and Service policy,
we can determine that a species (or a distinct population segment of a
vertebrate species) is an endangered or threatened species based on any
of five factors: (A) The present or threatened destruction,
modification, or curtailment of its habitat or range; (B)
overutilization for commercial, recreational, scientific, or
educational purposes; (C) disease or predation; (D) the inadequacy of
existing regulatory mechanisms; or (E) other natural or manmade factors
affecting its continued existence. We reviewed all available scientific
and commercial information pertaining to the five threat factors in our
evaluation of each species.
We have determined that the western yellow-billed cuckoo is
threatened by two of these five factors (A and E). We consider Factors
A and E to be the main threats to the species.
Factor A threats result from habitat destruction, modification, and
degradation from dam construction and operations; water diversions;
riverflow management; stream channelization and stabilization;
conversion to agricultural uses, such as crops and livestock grazing;
urban and transportation infrastructure; and increased incidence of
wildfire. These factors also contribute to fragmentation and promote
conversion to nonnative plant species, particularly tamarisk. The
threats affecting western yellow-billed cuckoo habitat are ongoing.
Such a loss of riparian habitat leads not only to a direct reduction in
yellow-billed cuckoo numbers but also leaves a highly fragmented
landscape, which can reduce breeding success through increased
predation rates and barriers to dispersal by juvenile and adult yellow-
billed cuckoos.
Factor E threats, including habitat rarity and small, isolated
populations of the western yellow-billed cuckoo, cause the remaining
populations in western North America to be increasingly susceptible to
further declines through lack of immigration, chance weather events,
fluctuating availability of prey populations, pesticides, collisions
with tall vertical structures during migration, spread of the
introduced tamarisk leaf beetle as a biocontrol agent in the Southwest,
and climate change. The ongoing threat of small overall population size
leads to an increased chance of local extinctions through random
events.
We will seek peer review. We are seeking comments and soliciting
information from knowledgeable individuals with scientific expertise to
review our analysis of the best available scientific and commercial
data and application of that information to improve this proposed rule.
Because we will consider all comments and information received during
the comment period, our final determinations may differ from this
proposal.
Information Requested
We intend that any final action resulting from this proposed rule
will be based on the best scientific and commercial data available and
be as accurate and as effective as possible. Therefore, we request
comments or information from the public, other concerned governmental
agencies, Native American tribes, the scientific community, industry,
or any other interested parties concerning this proposed rule. We
particularly seek comments concerning:
(1) The western yellow-billed cuckoo's biology, range, and
population trends, including:
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(a) Habitat requirements for feeding, breeding, and sheltering;
(b) Genetics and taxonomy;
(c) Historical and current range including distribution patterns;
(d) Historical and current population levels, and current and
projected trends;
(e) Past and ongoing conservation measures for the DPS, its
habitat, or both;
(f) Locations of any additional populations of western yellow-
billed cuckoo;
(g) Breeding season data in the mountain ranges of southeastern
Arizona and southwestern New Mexico;
(h) Breeding season data north and south of the United States in
Canada and Mexico; and
(i) Additional morphological and genetic data on yellow-billed
cuckoos along the DPS boundary in New Mexico and Texas.
(2) The factors that are the basis for making a listing
determination for a species under section 4(a) of the Act, which are:
(a) The present or threatened destruction, modification, or
curtailment of its habitat or range;
(b) Overutilization for commercial, recreational, scientific, or
educational purposes;
(c) Disease or predation;
(d) The inadequacy of existing regulatory mechanisms; or
(e) Other natural or manmade factors affecting its continued
existence.
(3) Biological, commercial trade, or other relevant data concerning
any threats (or lack thereof) to the western yellow-billed cuckoo, and
regulations that may be addressing those threats.
(4) Any information on the biological or ecological requirements,
and ongoing conservation measures for the western yellow-billed cuckoo
and its habitat including but not limited to any changes in dam
operations that may benefit the species or its habitat.
(5) Current or planned activities in the areas occupied by the
western yellow-billed cuckoo, and possible impacts of these activities
on the species or its habitat.
(6) Information on the projected and reasonably likely impacts of
climate change on the western yellow-billed cuckoo and its habitat.
Please include sufficient information with your submission (such as
scientific journal articles or other publications) to allow us to
verify any scientific or commercial information you include.
Please note that submissions merely stating support for or
opposition to the action under consideration without providing
supporting information, although noted, will not be considered in
making a determination, as section 4(b)(1)(A) of the Act directs that
determinations as to whether any species is a threatened or endangered
species must be made ``solely on the basis of the best scientific and
commercial data available.''
You may submit your comments and materials concerning this proposed
rule by one of the methods listed in the ADDRESSES section. We request
that you send comments only by the methods described in the ADDRESSES
section.
If you submit information via http://www.regulations.gov, your
entire submission--including any personal identifying information--will
be posted on the Web site. If your submission is made via a hardcopy
that includes personal identifying information, you may request at the
top of your document that we withhold this information from public
review. However, we cannot guarantee that we will be able to do so. We
will post all hardcopy submissions on http://www.regulations.gov.
Comments and materials we receive, as well as supporting
documentation we used in preparing this proposed rule, will be
available for public inspection on http://www.regulations.gov, or by
appointment, during normal business hours, at the U.S. Fish and
Wildlife Service, Sacramento Fish and Wildlife Office (see FOR FURTHER
INFORMATION CONTACT).
Previous Federal Actions
On February 9, 1998, we received a petition from the Southwest
Center for Biological Diversity (Center for Biological Diversity) on
behalf of 22 groups to list the yellow-billed cuckoo under the Act. The
petitioners stated that they believe the yellow-billed cuckoo ``is
endangered in a significant portion of its range (the western United
States).'' The petitioners also stated they ``believe this range of
endangerment is coterminous with a valid subspecies, the western
yellow-billed cuckoo (Coccyzus americanus occidentalis),'' and that
they would concur with a decision to list this taxon. Petitioners also
requested that critical habitat be designated for the yellow-billed
cuckoo concurrent with the listing, pursuant to 50 CFR 424.12 and the
Administrative Procedure Act (5 U.S.C. 553). The petition included
supporting information on the species relating to taxonomy, ecology,
adequacy of existing regulatory mechanisms, historical and present
distribution, current status, and threats in the western United States.
On February 17, 2000, we announced a 90-day petition finding in the
Federal Register (65 FR 8104) concluding that the petition presented
substantial scientific or commercial information to indicate that
further investigation, through a status review, was required to
determine the taxonomic validity of a western subspecies, and to
determine if listing the western population of the yellow-billed cuckoo
as a DPS may be warranted. In our finding, we noted that the petition
did not present sufficient information to indicate that listing of the
species as a whole may be warranted.
On July 25, 2001, we published a 12-month petition finding in the
Federal Register (66 FR 38611) concluding that the yellow-billed cuckoo
populations west of the Continental Divide constituted a valid DPS and
that the DPS was warranted for listing; however, this action was
precluded by higher priority listing actions, and the DPS was placed on
our candidate species list. The range of the DPS was identified to
include at least portions of 12 western States west of the crest of the
Rocky Mountains, with the Canadian and Mexican borders constituting the
northern and southern boundaries respectively. On October 30, 2001, a
list of new candidate species included the yellow-billed cuckoo,
western continental United States DPS, giving it a listing priority
number of 6 based on non-imminent threats of high magnitude (66 FR
54810, 54818) as defined by our policy on determining listing
priorities (48 FR 43098; September 21, 1983). In the 2005 candidate
notice of review document (70 FR 24875; May 11, 2005), the listing
priority number was upgraded from 6 to 3 based on reassessing the
nature of the threats as imminent and of a high magnitude. The 2011
notice indicated that preparation of a listing rule was under way (76
FR 66391; October 26, 2011).
On July 12, 2011, a court settlement, Center for Biological
Diversity v. Salazar, 10-cv-0230 required the Service to submit to the
Federal Register for publication either a proposed rule or a not-
warranted finding for the western yellow-billed cuckoo on or before
September 30, 2013.
Background
In this section of the proposed rule, it is our intent to discuss
only those topics directly relevant to the proposed listing of the
yellow-billed cuckoo in the western portions of the United States,
Canada, and Mexico as a threatened DPS.
Species Information
The yellow-billed cuckoo (Coccyzus americanus) is a member of the
avian family Cuculidae and is a Neotropical migrant bird that winters
in South
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America and breeds in North America. Yellow-billed cuckoos spend the
winter in South America, east of the Andes, primarily south of the
Amazon Basin in southern Brazil, Paraguay, Uruguay, eastern Bolivia,
and northern Argentina (Ehrlich et al. 1992, pp. 129-130; AOU 1998, p.
247; Johnson et al. 2008b, pp. 18-29). The breeding range of the entire
species formerly included most of North America from southeastern and
western Canada (southern Ontario and Quebec and southwestern British
Columbia) to the Greater Antilles and northern Mexico (AOU 1957, pp.
269-270; AOU 1983, p. 284; AOU 1998, p. 247).
Adult yellow-billed cuckoos have moderate to heavy bills, somewhat
elongated bodies, and a narrow yellow ring of colored bare skin around
the eye. The plumage is loose and grayish-brown above and white below,
with reddish primary flight feathers. The tail feathers are boldly
patterned with black and white below. They are a medium-sized bird
about 12 inches (in) (30 centimeters (cm)) in length, and about 2
ounces (oz) (60 grams (g)) in weight. The species has a slender, long-
tailed profile, with a fairly stout and slightly down-curved bill,
which is blue-black with yellow on the basal half of the lower
mandible. The legs are short and bluish-gray. Yellow-billed cuckoos
have a zygodactyl foot, in which two toes point forwards and two toes
point backwards. Juveniles resemble adults, except the tail patterning
is less distinct and the lower bill has little or no yellow. Males and
females differ slightly; the males have a slightly smaller body size,
smaller bill, and the white portions of the tail tend to form distinct
oval spots. In females the white spots are less distinct and tend to be
connected (Hughes 1999, pp. 2-3).
Typically a secretive and hard-to-detect bird, mated yellow-billed
cuckoos have a distinctive ``kowlp'' call, which is a loud, nonmusical
series of notes that slows down and slurs toward the end. Unmated
yellow-billed cuckoos advertise for a mate using a series of soft
``cooing'' notes. Both members of a pair use the ``knocker'' call, a
series of soft notes given as a contact or warning call near the nest
(Hughes 1999, pp. 8-9).
Little information exists on lifespan for yellow-billed cuckoos,
which is a result of the scarcity of banded yellow-billed cuckoos and a
very low recovery rate (0.4 percent) (Hughes 1999, p. 18). The longest
known lifespan of a banded yellow-billed cuckoo is 5 years (U.S.
Geological Survey (USGS) Patuxent Wildlife Research Center 2012, p. 1).
Taxonomy
The separation of yellow-billed cuckoos into subspecies was first
discussed by Ridgway (1887, p. 273) who separated the yellow-billed
cuckoo into an eastern (Coccyzus americanus americanus) and western (C.
a. occidentalis) subspecies, based on western birds being ``larger,
with proportionately larger and stouter bill.'' Ridgway's western
subspecies included birds from western Texas through the Great Basin
portions of Colorado and Wyoming, west and north to the Pacific coast
and southwestern British Columbia. Historically the western subspecies
was known as the California cuckoo (Ridgway 1887, p. 273; Belding 1890,
p. 57) or California yellow-billed cuckoo (Grinnell and Miller 1944,
pp. 186-187). Recently, in the literature, it has been called the
western yellow-billed cuckoo, a name we are using in this document to
refer to the DPS. Wetmore (1968, pp. 325-326) added that western
yellow-billed cuckoos are slightly grayer above, and eastern yellow-
billed cuckoos are browner. Oberholser and Kincaid (1974, pp. 434-435)
concurred with Ridgway and split the subspecies' range in western Texas
between the Rio Grande and the Pecos Rivers, west of Big Bend. The two
subspecies were generally included in ornithological treatments through
the 1970s (for example, American Ornithologists' Union (AOU) 1957, pp.
269-270; Oberholser and Kincaid 1974, pp. 434-435).
Some ornithologists have questioned the separation of the yellow-
billed cuckoo into two subspecies (Todd and Carriker 1922, pp. 209-213;
Swarth 1929, pp. 297-298; Van Tyne and Sutton 1937, p. 35; Bent 1940,
p. 67), citing the small magnitude and inconsistency of differences and
broad overlap in size between eastern and western birds. These
questions, however, were not based on systematic analysis of
geographical variation as it pertains to resolving the yellow-billed
cuckoo subspecies question. Since 1957, AOU checklists, the recognized
authority for taxonomy of North American birds, have not listed
subspecies, stating practical grounds (for example, space limitations),
and that the validity (in the sense of their distinguishability) of
many described avian subspecies still needs to be evaluated, as does
the potential for unrecognized subspecies (AOU 1983, p. 284; AOU 1998,
pp. 1-19). The most recent checklist (AOU 1998, pp. 1-19) refers
readers to the 1957 checklist (AOU 1957, pp. 269-270) for subspecies
taxonomy, which presents the yellow-billed cuckoo as comprising two
separate subspecies.
In response to a 1986 petition (52 FR 2239; January 21, 1987) to
list the yellow-billed cuckoo in the States of California, Washington,
Oregon, Idaho, and Nevada, we requested that Dr. Richard C. Banks, an
avian taxonomist and Fish and Wildlife Service employee at the National
Museum of Natural History, evaluate the validity of the subspecies. Dr.
Banks compared three morphological characteristics (bill length, depth
of upper mandible, and wing length) of almost 700 specimens of adult
yellow-billed cuckoos from throughout the species' range and visually
examined the colors of specimens. He found: (1) No pattern of
geographical variation in color; (2) substantial overlap between
eastern and western birds in wing length, bill length, and mandible
depth; and (3) no statistically significant differences for these three
characteristics. He concluded that the data did not justify the
separation into eastern and western subspecies (Banks 1988, pp. 473-
477). Subsequently, statistical errors were discovered in Banks' study
(Spiller 1988, pp. 1-3), and a reanalysis of the same data yielded
statistically significant differences (p<0.001) between eastern and
western yellow-billed cuckoos for the three characteristics measured by
Banks. Dr. Banks published a correction to his earlier paper (Banks
1990, p. 538), acknowledging the computational error and stating that
the ``statistical difference cannot be equated to a biological or
practical difference.'' In support of this, he cited the small
differences between mean measurements, the large degree of overlap
between eastern and western birds in the ranges of measurements for the
three characteristics he measured, and the sensitivity of the
statistical procedure to detect very small differences as
``significant,'' given the large sample sizes. His conclusion that the
species was monotypic remained unchanged (Banks 1990, p. 538).
Dr. Banks later provided his data to two avian ecologists (Franzreb
and Laymon 1993, pp. 17-28), who analyzed the same data set,
supplemented by measurements from an additional 41 specimens of western
birds and the inclusion of a fourth characteristic, tail length.
Franzreb and Laymon (1993, pp. 17-28), noting statistical errors by
Banks (1988, pp. 473-477), found that western birds are larger than
eastern birds. They developed a discriminant function analysis (DFA)
equation that correctly predicted origin for 83.8 percent of eastern
male and 74.6 percent of
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western male yellow-billed cuckoos, and for 89.6 percent of eastern and
85.8 percent of western female yellow-billed cuckoos. These predictive
DFA equations have been accepted as a useful tool to separate the
eastern and western populations by several researchers (Pyle 1997, pp.
56-57; Hughes 1999, p. 23; and Pruett et al. 2001, p. 229). Franzreb
and Laymon (1993, pp. 17-28) also analyzed behavioral and ecological
differences between western and eastern birds, and found differences in
the timing of migration and breeding, with western birds arriving on
breeding grounds later and laying eggs later than eastern birds at the
same latitude. They concluded that: (1) The recognition of subspecies
on the basis of measurements of existing specimens is equivocal; (2)
the study of geographical variation in vocalizations, bill color, and
genetics was needed; (3) the two subspecies should be retained pending
the above studies; and (4) ``because the western yellow-billed cuckoo
is so critically endangered . . . changes in its taxonomic
classification should be made only after the best possible study.''
In 2001, two separate research labs conducted studies on the
genetic differences between eastern and western yellow-billed cuckoos
(Fleischer 2001, pp. 14-16; Pruett et al. 2001, pp. 228-231), reaching
different conclusions regarding the taxonomic status of yellow-billed
cuckoos from the two regions. Fleischer examined two neutral regions of
the mitochondrial DNA (Control Region and ATPase subunit 8 regions) and
found no genetic structure that separated eastern from western yellow-
billed cuckoos, or supported subspecies or evolutionarily significant
unit (for example, a species, a subspecies, or a distinct population)
status for the species. He did suggest that an examination of markers
with higher mutation rates (for example, microsatellites) might reveal
significant genetic structure and suggested that microsatellite studies
be conducted.
Pruett et al. (2001, p. 229) examined a different region of the
mitochondrial DNA (cytochrome b), and came to a different conclusion
from Fleischer. They found substantial differences between the two
subspecies, and concluded that they were genetically distinct and had
diverged 205,000 to 465,000 years ago. They concluded that the western
yellow-billed cuckoo was an evolutionarily significant unit, probably
at the subspecies level, and that these results were particularly
significant because the differences were found on a gene that codes for
a protein important in cell respiration, not a neutral zone, meaning
that the differences were derived through selective evolutionary
pressure rather than chance events. However, their study was done with
a very small sample of specimens that did not cover the range of either
the eastern or western yellow-billed cuckoo.
Although mitochondrial analyses are routinely used in phylogenetic
studies, they have well-known limitations, sometimes lumping taxa that
are different or separating taxa that are the same (Funk and Omland
2003, p. 403). Farrell (2006, pp. 9-32) reexamined the subspecies
status of western yellow-billed cuckoo mitochondrial DNA with a larger
geographic distribution of samples representative of overall species
range with focused sampling effort on the zones of contact between the
eastern and western populations. Farrell's (2006, pp. 33-44) results
revealed only limited genetic divergence between eastern and western
populations of yellow-billed cuckoo and concluded that the sequences
used were not sufficiently variable to detect genetic differentiation
within this species. Genetic markers such as microsatellites in nuclear
DNA are ideal for population studies and preferable over mitochondrial
DNA sequence analysis due to their higher mutation rates and additional
information content. These studies, when conducted, may provide a
better understanding of genetics and geography variation in yellow-
billed cuckoo populations (Hailer et al. 2012, pp. 346-347).
However, Hughes (1999, pp. 1-27) concluded that size alone was
sufficient to separate the subspecies, and that the discriminant
function analysis equations developed by Franzreb and Laymon (1993, pp.
17-28), and used by Pyle (1997, pp. 56-57), worked to identify
individuals to subspecies level. She also concluded that: (1) The size
differences between the subspecies in western Texas and southern New
Mexico, the closest distance between eastern and western yellow-billed
cuckoos, were not gradual east to west and the change in size was too
abrupt to be clinal; (2) the difference in timing of migration and
breeding ``must have evolved independently for some time;'' and (3) the
eastern and western yellow-billed cuckoos were different taxa, probably
at the subspecies level (Hughes 2000, pp. 1-2).
In summary, the available genetic data regarding the
distinguishability of the western subspecies of the yellow-billed
cuckoo is conflicting. Since 2001, three genetic studies have been
completed on the yellow-billed cuckoo using mitochondrial DNA. Two of
the studies did not and one study did find significant differences
between eastern and western populations of the species. The reason for
the inconsistency is not known. It is possible that future research
using microsatellite markers that have higher mutation rates rather
than the slowly evolving mitochondrial DNA would better determine more
subtle genetic differences. Because of these inconsistencies the
available genetic data are not considered sufficient to distinguish the
subspecies. However, a large majority of yellow-billed cuckoo
individuals can be grouped into separate population segments along an
east-west divide by comparing morphological data. Similarly,
genetically controlled behavior, especially migration timing, also
appears to separate the species into two populations segments along an
east-west divide.
Thus, our review of the best scientific and commercial data
available indicates that some information suggests that the western
population segment described in the scientific literature as the
western yellow-billed cuckoo (Coccyzus americanus occidentalis) is
distinguishable at the subspecific level; however, there is enough
equivocality in the literature to conclude for the purposes of this
proposed rule that recognition of the subspecies is not justified at
this time. In the 12-month finding (66 FR 38611), we determined that
the population segment of the yellow-billed cuckoo that nests in the
portion of the United States west of the Continental Divide is a DPS
under the Act per our 1996 DPS Policy. Because it has been more than a
decade since we conducted that analysis, it is appropriate to
reevaluate the available data, including any new information, to
determine whether the population segment of yellow-billed cuckoos that
nest in western North America is a DPS under the Act. This evaluation
is presented below.
Distinct Vertebrate Population Segment Analysis
Under the Act, we must consider for listing any species,
subspecies, or, for vertebrates, any DPS of these taxa if there is
sufficient information to indicate that such action may be warranted.
To implement the measures prescribed by the Act and its Congressional
guidance, we (along with the National Marine Fisheries Service)
developed policy that addresses the recognition of DPSs for potential
listing actions (61 FR 4721; February 7, 1996). The policy allows for
more refined application of the Act that better reflects
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the biological needs of the taxon being considered, and avoids the
inclusion of entities that do not require its protective measures.
Before we can evaluate whether a given population segment is a DPS
under the Act, we must first determine if any population segments exist
for the vertebrate species. As discussed in the Taxonomy section above,
much of the available scientific information supports considering the
yellow-billed cuckoos that nest in western and eastern North America as
biologically separate population segments.
To establish the range of the population segment under
consideration, we used the area occupied by the western yellow-billed
cuckoo (the subspecies) originally defined by Ridgway (1887, p. 273)
and later refined by other researchers (AOU 1957, pp. 269-270;
Oberholser and Kincaid 1974, pp. 434-435; Hughes 1999, Figure 1). After
careful consideration of other possible population segment
configurations, we determined that the Continental Divide (generally
the crest of the Rocky Mountains based on watershed boundaries), the
watershed divide between the Rio Grande and Pecos River, and the
Chihuahuan Desert in Mexico was the best division between eastern and
western populations. The area that we are considering occupied by the
potential DPS for the yellow-billed cuckoo is closely aligned with the
traditionally defined range of the western yellow-billed cuckoo
subspecies as partially described in the July 25, 2001, 12-month
finding (66 FR 38611). Our goal is to determine if this western
population meets the criteria of a distinct population segment and, if
so, whether the range boundaries identified in the literature are
appropriate for the boundary of the DPS. This DPS analysis is based
solely on the range during the breeding season because the migration
route and winter range of western yellow-billed cuckoos are poorly
known.
The geographical breeding range of the yellow-billed cuckoo in
western North America includes suitable habitat within the low- to
moderate-elevation areas west of the crest of the Rocky Mountains in
Canada and the United States including the upper and middle Rio Grande,
the Colorado River Basin, the Sacramento and San Joaquin River systems,
the Columbia River system, and the Fraser River. In Mexico the range
includes the Cape Region of Baja California Sur, and river systems in
the Mexican States of Sonora, Sinaloa, western Chihuahua, and
northwestern Durango. Eastern yellow-billed cuckoos (Coccyzus
americanus americanus) breed east of the Rocky Mountains, north to
North Dakota and southern Ontario, Canada, and south to eastern Mexico,
and the islands of the Caribbean (AOU 1957, pp. 269-270) (Figure 1).
[GRAPHIC] [TIFF OMITTED] TP03OC13.031
Under our DPS policy, three elements are considered in a decision
regarding the status of a possible DPS as endangered or threatened
under the Act. The elements are: (1) Discreteness of the population
segment in relation to the remainder of the species to which it
belongs; (2) the significance of the population segment to the species
to
[[Page 61627]]
which it belongs; and (3) the population segment's conservation status
in relation to the Act's standards for listing. In other words, if we
determine that a population segment of a vertebrate species being
considered for listing is both discrete and significant, we would
conclude that it represents a DPS, and thus a ``species'' under section
3(16) of the Act, whereupon we would evaluate the level of threat to
the DPS based on the five listing factors established under section
4(a)(1) of the Act to determine whether listing the DPS as an
``endangered species'' or a ``threatened species'' is warranted.
Below, we evaluate under our DPS policy whether the population
segment of yellow-billed cuckoos that occurs in the western United
States, northwestern Mexico, and southwestern Canada qualifies as a DPS
under the Act.
Discreteness
Under our DPS Policy, a population segment of a vertebrate species
may be considered discrete if it satisfies either of the following two
conditions: (1) It is markedly separated from other populations of the
same taxon as a consequence of physical, physiological, ecological, or
behavioral factors (quantitative measures of genetic or morphological
discontinuity may provide evidence of this separation); or (2) it is
delimited by international governmental boundaries within which
significant differences in control of exploitation, management of
habitat, conservation status, or regulatory mechanisms exist that are
significant in light of section 4(a)(1)(D) of the Act.
The analysis of the population segment of the yellow-billed cuckoo
in western North America is based on the first of those two conditions,
the marked separation from other populations. From southwest British
Columbia along the Canadian border to the southern end of the Sangre de
Cristo Mountains in northern New Mexico, nesting yellow-billed cuckoos
in western North America are separated from nesting yellow-billed
cuckoos in eastern North America by the high-elevation zone of the
Rocky Mountains. Yellow-billed cuckoos breed both east and west of the
crest of the Rocky Mountains, where suitable habitat occurs (Johnsgard
1986, p. 201) (we define the crest of the Rocky Mountains and
Continental Divide as the high elevation zone between the drainages
flowing west and east in the U.S., Canada, and Mexico). The division
between the western and eastern population segments spans a distance of
about 2,200 miles (mi) (3,540 kilometers (km)) from southwest British
Columbia near the Canadian border along the crest of the Rocky
Mountains based on watershed boundaries, south along the Rio Grande-
Pecos Rivers watershed divide to the United States-Mexico border in the
Big Bend area of Texas, then into Mexico along the eastern and southern
boundaries of the State of Chihuahua south to the southern border of
the State of Durango and to the Pacific Ocean along the southern border
of the State of Sinaloa. The distance of separation between breeding
yellow-billed cuckoos in the east and west varies along this division
from 160 mi (257 km) to more than 400 mi (644 km), and consists
entirely of areas of unoccupied, unsuitable habitat for breeding
yellow-billed cuckoos. The one exception to this distance of separation
is along the Rio Grande in southwestern Texas in Brewster County, where
eastern yellow-billed cuckoos breed as far west as Rio Grande Village
and western yellow-billed cuckoos are found upstream along the river
approximately 50 mi (80 km) to the west.
Yellow-billed cuckoos historically bred at the southern tip of
Vancouver Island and in the Fraser River valley north to Kamloops in
southwestern British Columbia, Canada (Bent 1940, p. 64; Campbell et
al. 1990, p. 481). The species was apparently never common, with 23
records (18 specimen and 5 sight records) between 1881 and 1927. Two of
these observations were of pairs believed to be nesting but not
confirmed. Since the 1920s, the species has been recorded five times in
British Columbia, with four of those records occurring since 1990 from
the eastern half of the Province in areas not considered breeding
habitat (Campbell et al. 1990, p. 481; Siddle 1992, p. 1169; Cornell
Lab of Ornithology 2012). Today, the species is considered extirpated
as a breeder from the Province, but adult, nonbreeding individuals
still occur irregularly (British Columbia Conservation Data Centre
2013).
In the northern Rocky Mountains and northern Great Plains--from the
Canada border south through Colorado--the yellow-billed cuckoo is
``extremely rare and local'' as a breeding bird both east and west of
the Rocky Mountains (Hughes 1999, p. 3). While the species breeds
locally in river valleys in southern Idaho, southwestern Wyoming,
western Colorado, and in Utah (Hughes 1999, pp. 1-3), it is quite rare
or absent within the higher Rocky Mountains (Johnsgard 1986, p. 201).
An examination of the distributional records for the Rocky Mountain
region indicates that the area has had few records of yellow-billed
cuckoos and the species is even scarcer at elevations above
approximately 6,000 feet (ft) (1,850 meters (m)), and almost never
breeds above 7,000 ft (2,154 m) (Bailey 1928, pp. 307-309; Phillips et
al. 1964, p. 45; Bailey and Niedrach 1965, pp. 404-406; Johnsgard 1986,
p. 201; Corman and Magill 2000, pp. 10, 15; Howe and Hanberg 2000, p.
1-20). Exceptions to the elevational limit do occur and recent records
of yellow-billed cuckoos have been confirmed above 6,000 ft (1,850 m)
in the areas of Lower Green River Basin from the Seedskadee National
Wildlife Refuge (NWR) to the Flaming Gorge Reservoir and west to the
Bear River Drainage in Wyoming; along the Yampa River near Craig in
northwest Colorado, and the Rio Grande River near Del Norte, and San
Luis Valley of south-central Colorado; and the Henry's Fork River in
Utah and Wyoming. Nevertheless, most of the crest of the Rocky
Mountains includes a wide region of higher elevation where habitat for
the species does not occur. In Colorado and Wyoming the region above
6,000 ft (1,850 m) is typically more than 150 mi (240 km) wide on an
east-west axis (Oxford 1995, p. 82).
The separation of the yellow-billed cuckoo western population
segment from yellow-billed cuckoos in the eastern population segment
continues south along the crest of the Rockies into southern Colorado
and northern New Mexico, then the Rocky Mountains end and the
separation is along the watershed boundary between the Rio Grande and
the Pecos Rivers in central New Mexico (Sangre de Cristo Mountains),
and southwest Texas, terminating at the Rio Grande in the Big Bend
National Park. In this region, the eastern and western yellow-billed
cuckoo populations are separated by arid basins and isolated mountain
ranges that emerge from a high desert plateau. These mountain ranges
from north to south include the Sangre de Cristo Mountains and
Sacramento Mountains in central and southern New Mexico, the Guadalupe
Mountains and Delaware Mountains on the Texas-New Mexico border, and
the Davis Mountains, Del Norte Mountains, and Santiago Mountains in
western Texas south to the Chisos Mountains in the Big Bend National
Park on the border with Mexico.
In southern New Mexico and western Texas where western yellow-
billed cuckoos nest along the Rio Grande and eastern yellow-billed
cuckoos nest along the Pecos River, the geographical separation is as
little as 160 mi (257 km) and even closer along the Rio Grande (50 mi;
80 km). The closer proximity of western and eastern yellow-billed
[[Page 61628]]
cuckoos in this region may be caused in part by the lower height of the
mountain range being a less effective barrier (Hubbard 1978, p. 32;
Howe 1986, p. 2). Historically, this gap was wider, because the banks
of the Pecos River did not have riparian woodland and the area was not
used by the species. Today, the riverine habitat along the Pecos River
consists primarily of introduced tamarisk (Tamarix spp.), and it is
thought that yellow-billed cuckoos from eastern North America have
colonized the Pecos River system. Much of the area between the Pecos
River and the Rio Grande in New Mexico and Texas consists of internal
ephemeral drainages that are not connected to any major river systems
and have no riparian habitat. Considering these factors along with the
information on physical factors, we have included Texas west of the Rio
Grande-Pecos River watershed boundary within the range of the western
population. This physical division coincides with behavioral
differences between eastern and western yellow-billed cuckoos, as
discussed below.
South of the United States-Mexico border, yellow-billed cuckoos are
separated by extensive areas of desert that lack suitable nesting and
foraging habitat. In Mexico, the Chihuahuan Desert widens to 350 mi
(563 km), and includes nearly all of the States of Chihuahua and
Coahuila. There are very few records of yellow-billed cuckoos for this
region, and we are not aware of any nesting records for either State.
Suitable breeding habitat or connective riparian corridors are also
lacking. Published range maps for the species do not include the
eastern three-quarters of Chihuahua or the western three-quarters of
Coahuila as part of the species' breeding range (Howell and Webb 1995,
p. 347; Hughes 1999, p. 1). There are only 12 records of yellow-billed
cuckoos from Chihuahua: 11 specimens from the 1940s to 1960 and a sight
observation in 2003. There are only nine records of the species from
Coahuila: six specimen and three sight records (1958, 1988, and 2011).
Three of the specimens from Coahuila were identified as eastern yellow-
billed cuckoos on their museum records, and the remainder were not
identified to subspecies. Seven specimens from Chihuahua were
identified to subspecies and six of these were considered the western
subspecies. It is likely that many, if not most, of the records from
this region are of migrating yellow-billed cuckoos, as 16 are from May
to mid-June or from late September, and only 5 are from late June or
July, the primary breeding season.
From this information we concluded that the Chihuahua-Coahuila
border was the most biologically reasonable boundary for the population
segment. The boundary then follows the southern border of Chihuahua
west to the Continental Divide, then south along the divide through the
State of Durango and west along the southern border of Durango and
Sinaloa. There are no breeding season records for yellow-billed cuckoos
from the State of Nayarit or Jalisco or farther south along the Pacific
coast of Mexico. The species has occurred sporadically in the State of
Zacatecas, but the records are from east of the Continental Divide.
Eastern and western yellow-billed cuckoos are highly migratory and
the two populations may spend winters in overlapping regions in South
America. However, we do not have information to indicate that there is
anything more than an extremely low level of interchange (if any at
all) between the two populations during the breeding season. This
conclusion is supported by differences in habitat use and morphology,
which are genetically controlled traits, as discussed in the following
sections.
Although the Rocky Mountains and the Chihuahuan Desert may not
wholly prevent movement of yellow-billed cuckoos between the east and
west, especially in a migratory species that winters far to the south,
and moves thousands of miles between its wintering and breeding
grounds, the available information indicates that this mountain range
and desert substantially separates yellow-billed cuckoo populations
during the breeding season thereby effectively separating them into
discrete populations. The separation between yellow-billed cuckoo
population segments in the east and west is a physical one that is
maintained by their behavioral differences, which we discuss below.
Behavioral Discreteness
Data collected from publications and other sources demonstrate the
existence of behavioral differences between yellow-billed cuckoos in
the east and west.
Yellow-billed cuckoo populations in the east and west differ in the
timing of arrival on the breeding grounds in the spring. Yellow-billed
cuckoos in western North America arrive on the breeding grounds 4 to 8
weeks later than eastern yellow-billed cuckoos at similar latitude
(Franzreb and Laymon 1993, pp. 24-25; Hughes 1999, pp. 5-6, 12-13;
Laymon 2000, in. litt., pp. 15-16). Timing of spring migration and
arrival on the breeding grounds has been determined to be the result of
an evolved response under genetic control, and is likely caused by
east-west climatic, habitat, and food availability differences
(Cresswell et al. 2011, pp. 13-15). The watershed boundary between the
Rio Grande and the Pecos Rivers also appears to separate yellow-billed
cuckoos that arrive in spring migration earlier on the Pecos River and
those that arrive later on the Rio Grande in addition to separating
morphological differences.
Information, including timing of migration, indicates that yellow-
billed cuckoos from Texas west of the Pecos River (from the Rio Grande
upstream of Big Bend) and from northwestern Mexico (Chihuahua, Sonora,
Sinaloa, Durango, Baja California Sur) exhibit greater similarity to
yellow-billed cuckoos in western North America, and those on the Pecos
River in Texas and eastern Mexico (Coahuila, Nuevo Leon, Tamaulipas,
San Luis Potosi) are more similar to yellow-billed cuckoos in the east
(Wauer 1971, p. 96; Oberholser and Kincaid 1974, pp. 434-435; Franzreb
and Laymon 1993, pp. 17-28; Hughes 2000, pp. 1-2, 26; Sproul 2001, in
litt., pp. 1-5). Based on the best available science, the watershed
boundary between the Rio Grande and Pecos Rivers is the optimum
dividing line between eastern and western yellow-billed cuckoo in this
area.
Based on migration timing, yellow-billed cuckoos split into two
populations. This split occurs along the line that corresponds with the
traditional subspecies boundary (see Figure 1).
Discreteness Conclusion
The available information indicates that the yellow-billed cuckoo
population segment that occurs west of the Continental Divide in the
United States, in southwestern Canada, and in northwestern Mexico is
markedly separated from the eastern population segment of yellow-billed
cuckoo, including those that nest in eastern North America, eastern
Mexico, certain Caribbean Islands, and the Yucatan Peninsula. The
distribution of the western populations is markedly separated
physically (geographically) during the breeding season from the
distribution of other yellow-billed cuckoo populations by high
mountains, extensive desert, or nonhabitat areas with the shortest
geographical separation occurring across 160 mi (257 km) of desert
between the Pecos River and Rio Grande in southern New Mexico and
western Texas. Evidence
[[Page 61629]]
that this geographical separation between populations has been
consistent through time may be found in the differences in the two
populations' biology and morphology. Even in this area of closest
proximity, genetically controlled behavior available in the scientific
literature provides evidence of a biological separation between the
western populations and eastern populations.
Under our DPS policy, the standard for discreteness does not
require absolute separation because this can rarely be demonstrated for
any population of organism. The standard for discreteness is simply a
mechanism for the entity being considered for a DPS to be defined and
described. For the yellow-billed cuckoo populations in western North
America, we have met this standard, and, therefore, we consider the
western population segment of the yellow-billed cuckoo from southern
British Columbia, Canada south along the Continental Divide in the
United States into Mexico, and ending at the coast in the State of
Sinaloa, Mexico, to be discrete per our DPS policy. We conclude that
the western population segment of the yellow-billed cuckoo is discrete
from the remainder of the species because the yellow-billed cuckoo
population segment that nests west of the Continental Divide and in
northwestern Mexico is markedly separated geographically and
behaviorally from all other populations of yellow-billed cuckoo,
including those that nest in eastern North America.
Significance
Under our DPS policy, once we have determined that a population
segment is discrete, we consider its biological and ecological
significance to the larger taxon to which it belongs. Our DPS policy
provides several potential considerations that may demonstrate the
significance of a population segment to the remainder of its taxon,
including: (1) Evidence of the persistence of the discrete population
segment in an ecological setting unusual or unique for the taxon, (2)
evidence that loss of the discrete population segment would result in a
significant gap in the range of the taxon, (3) evidence that the
population segment represents the only surviving natural occurrence of
a taxon that may be more abundant elsewhere as an introduced population
outside its historic range, or (4) evidence that the discrete
population segment differs markedly from the remainder of the species
in its genetic characteristics.
We have found substantial evidence that two of these four
significance criteria (numbers 2 and 4) are met by the discrete
population segment of yellow-billed cuckoos that occurs west of the
Continental Divide. We address these significance factors below as they
relate to the population segment of yellow-billed cuckoos that nests
west of the Continental Divide and in northwestern Mexico. We focus on
whether the loss of this population segment would result in a
significant gap in the range of the taxon and evidence that the
discrete population segment differs from other population segments in
its genetic characteristics in demonstrating significance of the DPS.
Evidence indicates that loss of the discrete population segment
would result in a significant gap in the range of the taxon. An
extensive area would be without yellow-billed cuckoos if the western
population segment were lost. Seven entire states and substantial
portions of five additional states in the United States, and six states
in Mexico, that are currently occupied would have no breeding
populations of the species. Bird migration experts divide the North
American continent into four migratory flyways: the Atlantic,
Mississippi, Central, and Pacific. The range of the yellow-billed
cuckoo west of the Rocky Mountains covers the entire Pacific flyway and
half of the Central flyway. Additionally, the range of the yellow-
billed cuckoo west of the Rocky Mountains covers 1,350,000 square (sq)
mi (3,496,500 sq km), or approximately 40 percent of the lower 48
states. Even though the actual area occupied by the species in western
North America is less than the total area identified above, the
potential loss of the western population of the yellow-billed cuckoo
would constitute a significant gap in the range of the species in North
America.
Evidence That the Discrete Population Segment Differs Markedly From
Other Populations of the Species in Its Genetic Characteristics
Data collected from publications and other sources demonstrate the
existence of morphological and physiological differences between
yellow-billed cuckoos in the east and west. Morphologically, the
yellow-billed cuckoos in western North America are generally larger,
with significantly longer wings, longer tails, and longer and deeper
bills (Franzreb and Laymon 1993, p. 25). Banks, in a review of the
species taxonomic status (1988, pp. 473-477) grouped yellow-billed
cuckoo specimens into 19 regional groups, 7 in the western United
States and western Mexico, 10 in the eastern United States and eastern
Mexico, 1 in New Mexico, and 1 in the Caribbean. He found yellow-billed
cuckoos in the east to be uniform in measurement throughout their range
and yellow-billed cuckoos in the west to be uniform in measurements
throughout their range (Banks 1988, p. 475). Banks stated that the
change from smaller to larger yellow-billed cuckoos appeared to take
place in extreme western New Mexico or extreme eastern Arizona (Banks
1988 p. 476). A subsequent analysis, based on available specimens from
New Mexico and western Texas, showed the watershed boundary between the
Pecos River and the Rio Grande as the apparent boundary between the
smaller eastern and larger western birds, with a majority of yellow-
billed cuckoos on the Rio Grande above Big Bend being larger western
birds (63 percent, n=19) and the majority of yellow-billed cuckoos on
the Pecos River being smaller eastern birds (82 percent, n=11)
(Franzreb and Laymon 1993, p. 25). This is the only area where the
ranges of the western and eastern population segments are in close
proximity; elsewhere the two populations are separated by wide expanses
of unsuitable, unoccupied habitat (Figure 1).
Other physical and morphological differences exist between yellow-
billed cuckoos in the east and west, and provide additional evidence of
ecological significance. These include:
Yellow-billed cuckoos in western North America produce
larger eggs (1.2 percent longer, 0.6 percent wider, and 3.2 percent
heavier) with thicker eggshells (7.1 percent thicker) (Hughes 1999, p.
14), which is an evolved trait that would help yellow-billed cuckoos in
the west to cope with potential higher egg water loss in the hotter,
drier conditions of western North America (Hamilton and Hamilton 1965,
pp. 426-430; Ar et al. 1974, pp. 153-158; Rahn and Ar 1974, pp. 147-
152).
Juvenile yellow-billed cuckoos in the east have yellow
bills (Oberholser and Kincaid 1974, pp. 434-435), while juvenile
yellow-billed cuckoos in the west have all-black bills (Franzreb and
Laymon 1993, p. 26).
Adult yellow-billed cuckoos in the west have a lower
mandible that is orange-yellow, while yellow-billed cuckoos in the east
have lower mandibles that are bright yellow (Franzreb and Laymon 1993,
p. 26; Laymon 2000, in litt., p. 14).
As noted previously, adult yellow-billed cuckoos in the
west are larger and heavier, on average, than adult yellow-billed
cuckoos in the east. More than 80 percent of individuals can be
assigned to east or west based on morphological measurements. These
differences are discussed above in the ``Taxonomy''
[[Page 61630]]
section (Oberholser and Kincaid 1974, pp. 434-435; Banks 1988, pp. 473-
477; 1990, p. 538; Franzreb and Laymon 1993, pp. 17-28).
Information, including morphology, indicates that yellow-billed
cuckoos from Texas west of the Pecos River (from the Rio Grande
upstream of Big Bend) and from northwestern Mexico (Chihuahua, Sonora,
Sinaloa, Durango, Baja California Sur) exhibit greater similarity to
yellow-billed cuckoos in western North America, and those on the Pecos
River in Texas and eastern Mexico (Coahuila, Nuevo Leon, Tamaulipas,
San Luis Potosi) are more similar to yellow-billed cuckoos in the east
(Wauer 1971, p. 96; Oberholser and Kincaid 1974, pp. 434-435; Franzreb
and Laymon 1993, pp. 17-28; Hughes 2000, pp. 1-2, 26; Sproul 2001, in
litt., pp. 1-5). Based on the best available science, the watershed
boundary between the Rio Grande and Pecos Rivers is the optimum
dividing line between eastern and western yellow-billed cuckoo in this
area.
Based on morphological measurements, bill color of young and
adults, egg size and weight, and migration timing, yellow-billed
cuckoos split into two populations. This split occurs along the line
that corresponds with the traditional subspecies boundary (see Figure
1). Phenotypically expressed traits do present substantial evidence
that the western population segment of yellow-billed cuckoo differs
markedly from other populations of the species.
However, the strongest evidence of differences between yellow-
billed cuckoos in the western population segment and those of the east
in genetic characteristics is the difference in timing of migrations.
This difference can only have developed as an evolved trait in response
to environmental factors over a long period of time, and thus is
genetically linked (Cresswell et al. 2011, pp. 13-15). As previously
discussed, the difference in size of yellow-billed cuckoos between east
and west, as well as differences in size, weight, and shell thickness
of eggs, are also evolved genetically linked traits. As stated earlier,
researchers have developed methods using these phenotypic (outwardly
expressed) traits that correctly predicted separation for nearly 90
percent of yellow-billed cuckoos that were eastern, and up to
approximately 86 percent that were western (Franzreb and Laymon 1993,
pp. 17-28). Thus, based on the phenotypic traits, there is indirect
evidence that the discrete population segment differs markedly from
other populations of the species in its genetic characteristics.
Significance Conclusion
The best available information indicates that the discrete yellow-
billed cuckoo population segment that nests west of the Continental
Divide and in northwestern Mexico is important to the taxon to which it
belongs because: (1) Loss of the population segment would leave a
significant gap in the species' range (more than one third of the
species' range would be vacant); and (2) it differs markedly from other
yellow-billed cuckoo populations in morphology (western yellow-billed
cuckoos are larger) Therefore, we conclude that the western population
segment of the yellow-billed cuckoo is significant per our DPS Policy.
DPS Conclusion
Based on the best scientific and commercial data available on
distribution as well as behavioral and morphological characteristics of
the species, we have determined that the western population segment of
the yellow-billed cuckoo is both discrete and significant per our DPS
policy. Therefore, we conclude that the western population segment of
the yellow-billed cuckoo is a DPS, and thus a ``species'' under section
3(16) of the Act. We believe that we used the DPS authority
appropriately in our determination of biological and ecological
significance because we chose a population segment with a geographical
distribution that is biologically meaningful and at an appropriate
scope and scale to respond to the petitioners' request.
The term ``distinct population segment'' is not commonly used in
scientific discourse. As such, and in contrast to taxonomically defined
species and subspecies, there is no established name for the western
distinct population segment of the yellow-billed cuckoo in the
available literature; we will refer to this ``species'' (DPS) as the
western yellow-billed cuckoo. The range of the western yellow-billed
cuckoo in Canada includes the area of Vancouver Island and along the
Fraser River system upstream to Kamloops to the Rocky Mountains west of
the Continental Divide. In the United States the DPS includes the area
west of the Continental Divide, south through Montana, Wyoming,
Colorado, and along the watershed divide between the upper and middle
Rio Grande and Pecos Rivers in New Mexico and Texas, south to Big Bend
in southwestern Texas, and extending to the states of the west coast.
In Mexico, the DPS is the area west of the eastern and southern border
of the State of Chihuahua, west of the Continental Divide in the State
of Durango, and the southern border of the State of Sinaloa (Figure 2).
[[Page 61631]]
[GRAPHIC] [TIFF OMITTED] TP03OC13.032
Status Assessment for the Western Yellow-bled Cuckoo
Distribution
Breeding Range
Based on historical accounts, the western yellow-billed cuckoo was
widespread and locally common in California and Arizona, locally common
in a few river reaches in New Mexico, locally common in portions of
Oregon and Washington, generally local and uncommon in scattered
drainages of the arid and semiarid portions of western Colorado,
western Wyoming, Idaho, Nevada, and Utah, and probably uncommon and
local in southern British Columbia, Canada (AOU 1998, p. 247; Hughes
1999, p. 3). In the past 90 years, the species' range in the western
United States has contracted. The northern limit of breeding along the
west coast is now in the Sacramento Valley, California, though recent
surveys suggest a small, potentially breeding population exists in
coastal northern California on the Eel River (AOU 1998, p. 247; Hughes
1999, p. 3; McAllister 2010, pp. 1-2). The current northern breeding
limit in the western interior States is in southeastern Idaho.
Winter Range and Migration Routes
The winter range of the western yellow-billed cuckoo is poorly
known. Eastern and western yellow-billed cuckoos may intermingle on the
wintering grounds and in migration, or they may have separate wintering
areas and migration routes. Data provided by the U.S. Geological Survey
(USGS) Biological Resources Division, Bird Banding Laboratory (BBL)
from bird band returns to date have been insufficient to determine
wintering patterns for the western yellow-billed cuckoo (BBL 1998, in
litt., p. 1; USGS 2012, web search). A single western yellow-billed
cuckoo from the breeding population on the middle Rio Grande River in
New Mexico was recently equipped with a geolocator and recaptured a
year later near where it was originally tagged. Data from the
geolocator indicated that the yellow-billed cuckoo wintered in eastern
Bolivia, southwestern Brazil, Paraguay, and northeastern Argentina,
spending 5 months from late November through late April moving around
an area 1,243 mi (2,000 km) in length, 373 mi (600 km) in width, and
463,323 sq mi (1.2 million sq km) in extent (Sechrist et al. 2012, pp.
2-11). The light level geolocator is a 0.05-oz (1.5-g) recording
instrument used to determine flight paths of migrating birds. It
records the change in light levels at different latitudes and
longitudes, and stores the data. The bird must then be recaptured so
the time and location data can be downloaded and analyzed. The extent
to which the western yellow-billed cuckoo commingles with eastern
yellow-billed cuckoos during migration or while overwintering is
unknown. However, because mates are selected on the breeding grounds,
commingling in migration or in the winter does not affect the DPS
status of the western yellow-billed cuckoo.
Migration routes of the western yellow-billed cuckoo are also
poorly known. Miller (1950, p. 83) recorded a migrating flock of
yellow-billed cuckoos in the Cape region of Baja California Sur in late
May or early June. A fledgling
[[Page 61632]]
yellow-billed cuckoo that was banded in the South Fork Kern River
Valley in late July 1985 was found dead near Phoenix in early September
of the same year (BBL 1998, in litt., p. 2) indicating a southeastern
migratory direction. The yellow-billed cuckoo equipped with a
geolocator (Sechrist et al. 2012, pp. 2-11) traveled from the middle
Rio Grande River south to southern Sonora, Mexico, in late July, then
back north to the Rio Grande before migrating southeast through central
Texas and eastern Mexico in August and September, and Honduras, Panama,
and Columbia in October. In November, the bird traveled through the
upper Amazon Basin of southern Columbia and western Brazil before
flying to its wintering area later in November. During spring
migration, the yellow-billed cuckoo moved north into western Brazil in
early May, traveling throughout the month through Columbia, Venezuela,
and the Caribbean, including Haiti and Jamaica, before arriving on the
Yucatan Peninsula in Mexico on June 1. It then flew overland to the
lower Rio Grande before moving to the Conchos River in Chihuahua,
Mexico, in mid-June, and returned to the middle Rio Grande near its
original capture point in early July (Sechrist et al. 2012, pp. 2-11).
Life History Parameters
Migration Timing
The western yellow-billed cuckoo generally arrives on its breeding
grounds in mid-June. Available data from California, Arizona, and
western New Mexico indicate a small number of arrivals in May, but most
birds arrive in June and some do not arrive until early July (Gaines
and Laymon 1984, pp. 53-58; Hughes 1999, p. 5; Cornell Lab of
Ornithology 2012). In late summer, the birds begin their southbound
migration in mid-August, and most have left the breeding grounds by
mid-September (Gaines and Laymon 1984, pp. 53-58). Migration timing is
similar throughout the range of the western DPS (Hughes 1999, p. 5). As
mentioned previously, a yellow-billed cuckoo with a geolocator departed
its breeding grounds in the middle Rio Grande on August 28, 2009, and
arrived back on its breeding ground on June 14, 2010 (Sechrist et al.
2012, pp. 2-11).
Breeding Season
The western yellow-billed cuckoo's breeding season varies
regionally with the availability of its preferred food. Nesting peaks
later (mid-June through August) than in most co-occurring bird species,
and may be triggered by an abundance of cicadas (Cicadidae sp.),
katydids (Tettigoniidae sp.), caterpillars (Lepidoptera sp.), or other
large prey items that form the bulk of their diet (Hamilton and
Hamilton 1965, pp. 427-428; Rosenberg et al. 1982, p. 271). On the
South Fork Kern River, the primary food items fed to young were
caterpillars, tree frogs (Pseudacris regilla), katydids, and
grasshoppers (Caelifera sp.) (Laymon et al. 1997, p. 7). In Arizona,
cicadas are an important food source (Halterman 2009, p. 112).
In California and Arizona, yellow-billed cuckoos rarely begin
nesting before mid-June. Nesting in western North America continues
through August, and up to three broods can be raised in a season if the
prey base is sufficient (Laymon et al. 1997, p. 11; Halterman 2009, p.
77). First egg dates for 104 nests at the South Fork Kern River from
1985 to 2001 ranged from June 6 to August 5, and the peak of the
breeding season was between June 21 and July 20, with 82.5 percent of
the clutches initiated during that time period (Laymon and Halterman
1985, p. 33; Laymon and Halterman 1986, p. 12; Laymon et al. 1987, p.
10; Laymon and Whitfield 1988, p. 6; Laymon et al. 1989, p. 9; Laymon
1991, p. 8; Laymon et al. 1993, p. 10; Laymon et al. 1994, p. 9; Laymon
and Williams 1998, p. 6; Laymon and Williams 1999a, p. 7; Laymon and
Williams 1999b, p. 7; Laymon and Williams 2001, p. 7; Laymon and
Williams 2002, p. 8). Yellow-billed cuckoos may breed at multiple
disjunct locations in the same year, with birds nesting in the United
States and then nesting again in Sonora, Mexico (Rohwer et al. 2009,
pp. 19050-19055).
Reproduction
Yellow-billed cuckoos exhibit a variety of reproductive strategies
that are thought to increase population recruitment during years with
abundant food. Long-term research at the South Fork Kern River in
California shows that most pairs (approximately 70 percent) are
monogamous during a breeding attempt (Laymon 1998, p. 4). There are
instances of communal nesting, with two pairs laying eggs and tending
young in the same nest (Laymon 1998, p. 4). In approximately 30 percent
of nests, apparently unrelated helper males attend the nest. Yellow-
billed cuckoos regularly nest twice during a single breeding season
(double brood) and, during years of exceptionally abundant food, have
successfully raised three broods in a season. While the male mate tends
the young of the first nest, the female can initiate a second clutch
either with the same mate or with a new male (Laymon et al. 1997, pp.
6-7; Halterman 2009, p. 114).
Yellow-billed cuckoos build an open cup nest with a loose saucer-
shaped stick construction. Both parents build the nest, incubate, and
tend the young. Clutch size varies from two to five eggs depending on
the available food supply. The incubation and nestling periods are
short, with the eggs hatching in 11-12 days and young fledging in 5-7
days. Incubation begins when the first egg is laid and the young hatch
asynchronously, with the oldest near fledging while the youngest has
just hatched (Hughes 1999, p. 15).
Nesting success is high in comparison to other open-cup nesting
birds (Laymon et al. 1997, p. 11). On the South Fork Kern River from
1985 to 2001, of 104 nests that were monitored, 92 (88 percent)
successfully produced at least one young and 76 percent of eggs laid
produced fledged young (Laymon and Williams 2002, p. 8). On the Bill
Williams River in western Arizona from 1993 to 2000, of 20 nests that
were monitored, 16 (80 percent) successfully produced at least one
young and 72 percent of the eggs laid produced fledged young (Halterman
2001, p. 26). Another study on the lower Colorado and Bill Williams
Rivers from 2008 to 2011, found that, of 59 nests monitored, 73 percent
were successful in fledging at least one young (Bill Williams River,
100 percent; lower Colorado River, 59 percent) (McNeil et al. 2012, pp.
49-54). On the San Pedro River in southeastern Arizona from 2001 to
2005, of 83 nests that were monitored, 58 (70 percent) successfully
fledged at least one young (Halterman 2002, p. 11; Halterman 2003, p.
11; Halterman 2004, p. 12; Halterman 2005, p. 10; Halterman 2006, pp.
10-11).
Breeding Site Fidelity
Breeding site fidelity, whether yellow-billed cuckoos return to
breed in the same area in which they hatched or nested in a previous
year, is difficult to study. Banding birds with unique combination of
bands is a way for researchers to track individuals through time,
allowing them to determine whether an individual has returned to the
same area. However, yellow-billed cuckoos often perch in dense foliage
and have short legs that are often covered by body feathers, so bands
are hard to see. As a result, there is a limited amount of information
on site fidelity.
The available data show that adults and nestlings do return to the
same or nearby nesting sites in successive years (Laymon 1998, p. 6).
For example, along the San Pedro River in Arizona, Halterman (2009, p.
77) re-sighted 5 of
[[Page 61633]]
52 (9.6 percent) yellow-billed cuckoos banded between 2001 and 2005. On
the Colorado River in California and Arizona, 4 of 14 yellow-billed
cuckoos (31 percent) banded in 2009 were re-sighted in 2010, and 7 of
51 yellow-billed cuckoos (11.8 percent) banded in 2010 were re-sighted
in 2011 (McNeil et al. 2011, p. 32; McNeil et al. 2012, p. 63). Banded
male yellow-billed cuckoos on both the Colorado and Kern Rivers have
returned to the same area to breed for three consecutive seasons
(Laymon 1998, p. 6; McNeil et al. 2011, p. 32; McNeil et al. 2012, p.
63). Two female yellow-billed cuckoos dispersed 21 and 24 mi (33 and 38
km) to other sites along the same reach of the Colorado River (McNeil
et al. 2012, p. 74). They also report a relatively high re-sight rate
of 13 percent among returning yellow-billed cuckoos banded as chicks in
2010 and returning as adults in 2011 (McNeil et al. 2012, pp. 73-74).
Conversely, the dramatic fluctuation in breeding pairs at long-term
study sites indicates that year-to-year movement between potential
breeding areas also occurs. On the South Fork Kern River from 1985 to
2000, the population increased from a low of 2 pairs in 1990 to a high
of 24 pairs in 1992, an increase that could not have come totally from
local population growth and recruitment (Laymon and Williams 2001, p.
9). On the Bill Williams River from 1993 to 2002, the population varied
from a low of 9 pairs or less in 1999 to a high of more than 28 pairs
in 2001, again, an increase that unlikely came entirely from local
population growth and recruitment (Halterman 2003, p. 31). In addition,
geolocator data from the cuckoo on the middle Rio Grande indicates that
the species can make long-distance movements during the breeding season
(Sechrist et al. 2012, pp. 2-11). It is likely that cuckoos return to
sites of previous successful breeding, but, if the conditions are not
suitable that year they move to other potential breeding sites.
Habitat Use and Needs
The western yellow-billed cuckoo currently nests almost exclusively
in low to moderate elevation riparian woodlands that cover 50 acres
(ac) (20 hectares (ha)) or more within arid to semiarid landscapes
(Hughes 1999, p. 6). Biologists have hypothesized that yellow-billed
cuckoos may be restricted to these extensive, moist habitats because of
humidity requirements for successful hatching and rearing of young
(Hamilton and Hamilton 1965, p. 427; Gaines and Laymon 1984, pp. 75-76;
Rosenberg et al. 1991 pp. 203-204). In California, Grinnell and Miller
(1944, pp. 186-187) described the yellow-billed cuckoo habitat as
``riparian jungles of willows of fairly old growth, often mixed with
Fremont cottonwoods (Populus fremontii), and with a tangled `lower
story' of blackberry (Rubus sp.), nettles (Urtica sp.), or wild grape
(Vitis californica).'' In other portions of the range, narrow-leaf
cottonwood (Populus augustifolia) and mesquite (Prosopis spp.) are
important habitat component (Righter et al. 2004, p. 82; Saab 1999, pp.
136-137). Occupied habitat in Arizona may also contain box elder (Acer
negundo), Arizona alder (Alnus oblongifolia), Arizona walnut (Juglans
major), Arizona sycamore (Platanus wrightii), oak (Quercus spp.),
netleaf hackberry (Celtis reticulata), velvet ash (Fraxinus velutina),
Mexican elderberry (Sambuccus mexicanus), tamarisk (Tamarix spp.; also
called salt cedar), and seepwillow (Baccharis glutinosa) (Corman and
Magill 2000, p. 5). Surveys conducted by the Arizona Breeding Bird
Atlas (Corman and Wise-Gervais 2005, p. 202) reported 68 percent of the
yellow-billed cuckoo observations were in lowland riparian woodlands,
often containing a variable combination of Fremont cottonwood, willow,
velvet ash, Arizona walnut, mesquite, and tamarisk.
Throughout the western DPS range, a large majority of nests are
placed in willow trees, but alder (Alnus spp.), cottonwood, mesquite,
walnut (Juglans spp.), box elder, sycamore, and tamarisk are also used
(Jay 1911, pp. 69-73; Hanna 1937, p. 58; Laymon 1980, p. 12; Halterman
and Laymon 1995, pp. 15-16; Corman and Magill, p. 16; Holmes et al.
2008, p. 21). Most nests are placed on well-foliaged horizontal
branches at sites with dense canopy cover above the nest (Laymon et al.
1997, pp. 7-8).
Western yellow-billed cuckoos require large blocks of riparian
habitat for breeding. Home ranges are large, vary in size depending on
seasonal food abundance, and overlap greatly both between members of a
pair and between neighboring pairs. At the landscape level, the amount
of cottonwood-willow-dominated vegetation cover and the width of
riparian habitat influences western yellow-billed cuckoo distribution
and abundance (Gaines and Laymon 1984, p.76). In California, yellow-
billed cuckoos are most likely to be found in patches of willow-
cottonwood riparian habitat greater than 200 ac (81 ha) in size.
Yellow-billed cuckoos rarely used smaller patches of habitat,
particularly when they were distantly isolated from other patches of
riparian habitat (Laymon and Halterman 1989, pp. 274-275). On the
Sacramento River, size of site, amount of riparian habitat in each 5-mi
(8-km) river segment, and presence of young woody vegetation were the
most important factors in a model explaining the distribution of
yellow-billed cuckoo pairs (Halterman 1991, p. 30). On the lower
Colorado River, in a comparison of occupied versus unoccupied habitat,
yellow-billed cuckoos were found at sites with denser riparian
vegetation and more variation in vegetation density, and less tamarisk
and shrubby vegetation, compared to unoccupied sites (Johnson et al.
2012, pp. 15-17).
Recent radio telemetry studies on the Rio Grande in New Mexico, the
San Pedro River in Arizona, and the Colorado River in Arizona and
California have shown that yellow-billed cuckoos use large home ranges
of 204 ac (82 ha), 125 ac (51 ha), and 95 ac (38 ha), respectively
(Halterman 2009, p. 93; Sechrist et al. 2009, p. vii; McNeil et al.
2010, p. 75; McNeil et al. 2011, p. 37; and McNeil et al. 2012, p. 69).
Breeding densities on the South Fork Kern River, where intensive
surveys for yellow-billed cuckoos were conducted for 17 years, averaged
0.81 pairs per 100 ac (40 ha) (Laymon et al. 1997, p. 19; Laymon and
Williams 2002, p. 5), which means they had home ranges of about 123 ac
(50 ha) on average.
On the Verde River in Arizona, sites occupied by yellow-billed
cuckoos were composed of deciduous riparian habitat at least 325 ft
(100 m) in width, dominated by Fremont cottonwood, Goodding's willow
(Salix gooddingii), Arizona alder, and Arizona sycamore, often adjacent
to patches of mesquite (Holmes et al. 2008, p. 27).
In Sonora, Mexico, yellow-billed cuckoos were summer residents in
willow-cottonwood riparian woodland, older mesquite woodland, tropical
deciduous forest, and tropical thorn scrub habitats (Russell and Monson
1998, p. 131). In southern Sonora, Mexico, Short (1974, p. 24) found
the yellow-billed cuckoos breeding in upland thorn forest, but they
were more common in the riparian zone. In a study focusing on cactus
ferruginous pygmy-owls (Glaucidium brasilianum cactorum) during late
spring and summer from 2001 through 2010, Flesch (2012 in litt.) found
yellow-billed cuckoos at 95 sites from June to September at elevations
from 328 to 6,902 ft (100 to 2,104 m). The number of birds at each site
ranged from 1 to 15 individuals. Flesch also confirmed breeding at four
sites in thornscrub habitats and at one site in upland Sonoran Desert
habitat. These records indicate a broader use of habitat by
[[Page 61634]]
yellow-billed cuckoos in Sonora, Mexico, possibly as a result of more
humid conditions caused by increased summer rainfall.
Little information is available on the foraging habitat of the
western yellow-billed cuckoos. Laymon (1980, p. 6) found that yellow-
billed cuckoos nesting along the Sacramento River in English walnut
orchards captured 88 percent of their food in riparian habitat,
foraging primarily in cottonwoods, willows, and white alders (Laymon
1980, pp. 16-18). On the South Fork Kern River, yellow-billed cuckoos
foraged primarily in cottonwood and willow woodlands with abundant
leafy vegetation (high foliage volume) (Laymon and Halterman 1985, p.
11). High foliage volume of cottonwoods appeared to be an important
characteristic of foraging sites, a parameter also noted by researchers
studying yellow-billed cuckoos along the Colorado River (Rosenberg et
al. 1991, pp. 203-204).
Little is known about migratory habitat for the western yellow-
billed cuckoo. Yellow-billed cuckoos may be found in a variety of
vegetation types during migration, including coastal scrub, secondary
growth woodland, hedgerows, humid lowland forests, and forest edges
from sea level to 8,125 ft (2,500 m) (Hughes 1999, pp. 6-7).
Additionally, during migration they may be found in smaller riparian
patches than those in which they typically nest. An account of a
migrating flock of yellow-billed cuckoos from the Cape region of Baja
California Sur documented them using mesquite scrub woodland (Miller
1950, p. 83). This variety of vegetation types suggests that the
habitat needs of the yellow-billed cuckoo during migration are not as
restricted as their habitat needs when nesting and tending young.
Wintering habitat of the western yellow-billed cuckoo is poorly
known. The species as a whole winters in woody vegetation bordering
fresh water in the lowlands to 1,500 m (4,921 ft), including dense
scrub, deciduous broadleaf forest, gallery forest, secondary forest,
subhumid and scrub forest, and arid and semiarid forest edges (Hughes
1999, p. 7).
Historical and Current Status
Populations of the western yellow-billed cuckoo are too small and
isolated in inaccessible habitat patches to be effectively sampled or
analyzed for trends by the USGS Breeding Bird Survey (BBS) program,
which is conducted atpoint count along roads. In the eastern United
States and Canada, where BBS data can be used to analyze yellow-billed
populations, these populations have declined by 59 to 67 percent over
the past 43 years (USGS 2012). This decline has been linked to both the
North Atlantic Oscillation and the El Ni[ntilde]o Southern Oscillation,
as well as to rising local temperatures (Anders and Post 2006, pp. 221-
227). For the western yellow-billed cuckoo, only information from
regional and local sources is available to determine population trends.
Pacific Northwest
In the Pacific Northwest, including Oregon, Washington, and British
Columbia, Canada, the western yellow-billed cuckoo was formerly fairly
common locally in cottonwood and willow bottoms along the Willamette
and lower Columbia Rivers in Oregon and Washington, and in the Puget
Sound lowlands of Washington (Jewett et al. 1953, pp. 342-343;
Gabrielson and Jewett 1970, pp. 329-330; Roberson 1980, pp. 225-226;
Marshall 1996, pp. 1-2; Marshall et al. 2003, p. 306). They were also
found locally in southwestern British Columbia (Hughes 1999, p. 4), but
the available data are not adequate to determine historical abundance.
Yellow-billed cuckoos were rare east of the Cascade Mountains in these
States and Province (Campbell et al. 1990, p. 481; Marshall et al.
2003, p. 306; Wahl et al. 2005, p. 210).
In Oregon, the last confirmed breeding records are from the 1940s.
Historically, western yellow-billed cuckoo were considered rare in the
State, both in the Willamette Valley, along the lower Columbia River,
and in eastern Oregon along the Snake River, although they were fairly
common along the Columbia River from 1923 to 1925 (Gabrielson and
Jewett 1970, pp. 329-330). Between 1970 and 1977, four yellow-billed
cuckoo sightings were made west of the Cascade Mountains in the
Willamette Valley (Gilligan 1994, pp. 162-163). Between 1970 and 1994
at least 20 yellow-billed cuckoos have been sighted east of the Cascade
Mountains (Gilligan 1994, pp. 162-163). A 1988 survey in eastern Oregon
and Klamath County located no yellow-billed cuckoos, but identified
potential breeding habitat along the lower Owyhee River (Littlefield
1988, p. 34). Recent records from 1990 to 2009 are primarily from May
and June and from the east side of the Cascades in Deschutes, Malheur,
and Harney Counties (Johnson and O'Neil 2001, pp. 460-461; Cornell Lab
of Ornithology 2012). Yellow-billed cuckoos were previously considered
a rare annual visitor in Harney County at isolated groves of trees
known as vagrant traps and the Malheur NWR (Altman 2001 pers. comm.),
but in the last decade it has not been a regular visitor (Marshall et
al. 2003, p. 306).
Recent records from the west side of the Cascades at the Sandy
River Delta near its confluence with the Columbia River in July of
2009, 2010, and 2012 (Withgott 2012, in. litt.; Leal 2012, in. litt.)
were the first observations of the species west of the Cascades since
1977. In June 2010 during surveys on the Columbia River a possible
cuckoo response was heard at Wallace Island, Columbia County, but the
sighting could not be verified (Flotlin 2011). Up to 87 percent of
wetland and riparian habitat have been lost in the Willamette Valley
due to agricultural practices and urbanization (Roth et al. 2004). The
available data suggest that if yellow-billed cuckoos still breed in
Oregon the numbers are extremely low, with pairs numbering in the
single digits.
In Washington, the last confirmed breeding records of yellow-billed
cuckoos are from the 1930s, and it is likely to have been extirpated as
a breeder in the State. Of the 24 records between 1836 and 1940 (9 egg
sets, 7 specimens, and 8 sight records), 23 were found west and one
east of the Cascades. The Washington Department of Fish and Wildlife
ranks the species as having historical occurrences only but still
expected to occur in the State. Incidental sightings have occurred
throughout the State, and the possibility of a vestigial breeding
population may still exist (Wahl et al. 2005, p. 210). Researchers made
17 records from 1956 to 2012, of which 13 were east of the Cascades.
The yellow-billed cuckoo is currently a candidate species for State
listing as threatened or endangered (Washington Natural Heritage
Program 2009, pp. 9, 35). Exploratory surveys have been conducted in
Okanogan, Yakima, Cowlitz, and Wahkiakum Counties in recent years to
check locations of previous sightings (Okanogan County) and potential
habitat (Yakima, Cowlitz, and Wahkiakum Counties), but no yellow-billed
cuckoos have been positively detected (Salzer 2010, pp. 1-3; Flotlin
2011, pp. 1-2); however, protocol level surveys have not been
conducted. There are few remaining examples, none of which are
extensive, of the river floodplain habitats bordering Puget Sound,
which historically had the most yellow-billed cuckoo sightings in the
State (King County 2007, p. 2). The available data suggest that if
yellow-billed cuckoos still breed in Washington, the numbers are
extremely low, with pairs numbering in the single digits.
[[Page 61635]]
Yellow-billed cuckoos historically occurred in southwest British
Columbia, Canada, in the vicinity of Victoria on Vancouver Island and
along the Fraser River system from Vancouver upstream to Kamloops (Bent
1940, p. 64; Campbell et al. 1990, p. 481). The species was apparently
never common, with 23 records (18 specimen and 5 sight records) between
1881 and 1927. Two of these observations were of pairs believed to be
nesting. The species has been recorded five times in British Columbia
since the 1920s, with four of those records from the eastern half of
the Province where historically the species had not been observed
(Campbell et al 1990, p. 481; Siddle 1992, p. 1169; Cornell Lab of
Ornithology 2012). As mentioned previously, the species is considered
as an extirpated breeder in the Province and is still very rare based
on reported observations (British Columbia Conservation Data Centre
2013).
Montana
We have very limited data for yellow-billed cuckoos from the area
west of the Continental Divide in Montana. Three specimens have been
collected since the early 1960s, and there are few recorded sightings
since the early 1900s (Saunders 1921, p. 174). A few records indicate
that yellow-billed cuckoos occurred around the Flathead River area, but
there are no confirmed breeding records (Lenard 2001, pp. 1-3).
Potential habitat within the range of the western yellow-billed cuckoo
in Montana is very limited, and it is unlikely that a breeding
population exists within the State.
Idaho
In Idaho, the yellow-billed cuckoo is considered a rare visitor and
local summer resident that occurs in scattered drainages, primarily in
the southeastern portion of the State (Burleigh 1972, p. 159; Idaho
Fish and Game 2005, pp. 222-223; Cavallaro 2011, entire). In northern
and central Idaho, there were only four records of yellow-billed
cuckoos during the 20th century (Taylor 2000, p. 252). Reynolds and
Hinckley (2005, p. 5) concluded that the few sightings in northern
Idaho are most likely of transient, nomadic, or migrant individuals;
with no data suggesting that the species historically or currently
nests there. In southwestern Idaho the yellow-billed cuckoo has
historically been considered a rare summer visitor and breeder in the
Snake River Valley (Idaho Fish and Game 2005, p. 223).
Recent records are primarily from the southeastern portion of the
State along the South Fork of the Snake River (Stephens and Sturts
1997, p. 36; Taylor 2000, pp. 252-254; Reynolds and Hinckley 2005, p.
7; Cavallaro 2011, entire). Taylor (2000, pp. 252-254), in his 2000
review of the status of the species in Idaho, concluded that they had
declined greatly as a breeding bird in the State, and that there were
currently fewer than a few dozen breeding pairs and possibly fewer than
10. More recent surveys of yellow-billed cuckoos continue to show the
majority of sightings are in the Snake River corridor in southeast
Idaho with few or no sightings in other areas where the yellow-billed
cuckoo had been historically observed (Reynolds and Hinckley 2005, p.
7; Cavallaro 2011, p. 3). In addition, yellow-billed cuckoos likely
nested in south-central Idaho near Stanton Crossing, Blaine County, in
2003 and 2004 (Reynolds and Hinckley 2005, p. 7). A survey in 2009 near
Magic Lake on the Big Wood River located a singing male in a location
that was previously unknown (Carlisle and Ware 2010, p. 4). Follow-up
surveys in 2010 along the Big Wood River and Little Wood River failed
to detect any yellow-billed cuckoos (Carlisle and Ware 2010, p. 12).
The most recent statewide assessment estimated the breeding population
in Idaho is likely limited to no more than 10 to 20 breeding pairs in
the Snake River Basin (Reynolds and Hinckley 2005, p. 7).
Wyoming
Historically, yellow-billed cuckoos were rare and local in Wyoming.
Knight (1902, p. 86), in his summary of the birds of Wyoming, did not
include the species on the State's list, and Grave and Walker (1913, p.
46) reported only one record for the State. Prior to 2001, the
distribution of yellow-billed cuckoos from summer records of the
Wyoming Natural Heritage Database showed a few scattered sightings,
with only 12 records from southwestern Wyoming (Bennett and Keinath
2001, pp. 9, 17). Currently, yellow-billed cuckoo occurs on the western
side of the Rocky Mountains along the Lower Green River Basin from the
Seedskadee NWR to the Flaming Gorge Reservoir and west to the Bear
River Drainage. Within the range of the DPS defined in this document,
breeding activity is unconfirmed in Wyoming, but observations suggest
that nesting may occur within the Green River Basin and along the Snake
River within the State (Deibert 2001, pers. comm., pp. 1-16). On July
4, 2003 a yellow-billed cuckoo was found by Wyoming Game and Fish
Department in the town of Green River after it collided with a window
of their office building (Wyoming Natural Diversity Database 2003
(WYNDD)). In July 2003, yellow-billed cuckoo surveys were conducted at
the Seedskadee NWR and on July 10, 2003, a yellow-billed cuckoo near
Big Island in Seedskadee NWR responded with `kowlp' calls to a recorded
play-back call (Sweanor pers comm., WYNDD 2003). Call-back surveys were
again conducted near Big Island in 2004 by Service personnel.
Subsequently, one observation was made of a yellow-billed cuckoo in
2005 and three cuckoos were observed in 2006 near Big Island,
Seedskadee NWR (Seedskadee NWR, unpublished reports). No other recent
surveys have been done (Beason 2010, pp. 2-3). The available literature
suggests that the breeding population of the yellow-billed cuckoo
within the State is extremely low, numbering in the single digits, and
potential nesting habitat is very limited. Therefore, we conclude that
the western yellow-billed cuckoo occurs in very small numbers as a
breeder in Wyoming, with likely fewer than five breeding pairs.
Colorado
West of the Continental Divide in Colorado, the yellow-billed
cuckoo was probably never common (Bailey and Niedrach 1965, pp. 404-
406), and it is now extremely rare (Kingery 1998, pp. 204-205). Yellow-
billed cuckoos were found along the Colorado River in Palisade, near
Grand Junction (Mesa County), annually through the 1950s and 1960s
(Righter et al. 2004, p. 82). Yellow-billed cuckoos were also regularly
detected as recently as the mid-1980s along the Uncompahgre and
Gunnison Rivers near Delta (Delta County) (Beason 2010, p. 1).
In 1998, the Colorado Breeding Bird Atlas (Kingery 1998, pp. 204-
205) gave the general status of the yellow-billed cuckoo in Colorado as
nearly extirpated in the western half of the State. During the 1987 to
1994 period covered by the Atlas, only three yellow-billed cuckoos were
recorded on the western slope, with one confirmed nesting observation
along the Yampa River near Hayden in 1988. Other confirmed nesting
records (mid-1980s) were associated with outbreaks of caterpillars in
box elders in the Four Corners region and Durango area (Colyer 2001,
pp. 1-6). National Park Service surveys in southwest Colorado from 1988
through 1995 for the Colorado Bird Breeding Atlas provided no records
of yellow-billed cuckoos.
In 1998, biologists conducted focused yellow-billed cuckoo surveys
along 242 mi (389 km) of lowland river riparian habitat along six
rivers in west-central Colorado. They found one probable
[[Page 61636]]
nesting pair (Dexter 1998, p. 3). Reports of single yellow-billed
cuckoos have come primarily from the Grand Junction area and Mesa
County in 2001, 2002, 2005, 2008, and 2011, with a report of more than
one yellow-billed cuckoo at Orchard Mesa Wildlife Area in 2006 (Beason
2010, p. 1; Beason 2012, p. 5). Additional reports include one yellow-
billed cuckoo south of Montrose in Montrose County near the Uncompahgre
River in 2009, one yellow-billed cuckoo along the Gunnison River near
Gunnison in 2007 (Beason 2010, p. 1), and detections by the Rocky
Mountain Bird Observatory along the Yampa River near Craig in 2007 and
2008 and in far western Colorado near Nucla in 2005 and 2008 (Beason
2010, p. 1). However, surveys repeated near Craig and Nucla in 2009
failed to detect yellow-billed cuckoos. Since 2003, yellow-billed
cuckoos have been detected annually at the North Fork of the Gunnison
River Valley of west-central Colorado in Delta County, and breeding was
confirmed in 2008 and again in 2011 near Hotchkiss (Beason 2010, p. 1;
Beason 2012, p. 5).
Yellow-billed cuckoos have been detected annually since 2001 in the
San Luis Valley of south-central Colorado in Conejos County where
breeding is suspected, but not confirmed (Beason 2010, p. 1). Surveys
conducted on the Rio Grande near Del Norte, Rio Grande County, in 2008
and 2011 found yellow-billed cuckoos at several locations (Wildlife
Specialties, LLC, 2008; Rawinski 2011). Surveys by the Rocky Mountain
Bird Observatory in 2010 were conducted near historical detections and
at sites with suitable habitat in Archuleta, Conejos, Montezuma, and
Rio Grande Counties in south-central and southwest Colorado; no yellow-
billed cuckoos were detected (Beason 2010, p. 2). Survey results and
the available literature indicate an extremely small breeding
population of yellow-billed cuckoos in western Colorado. Therefore, we
conclude that the population of breeding pairs numbers in the low
single digits in the State.
Utah
Historically yellow-billed cuckoos were uncommon in Utah in
woodlands along streams in the lower valleys, especially the Salt Lake
Valley (Hayward et al. 1976, p. 107). There are scattered records for
the State, mainly from the vicinity of Provo, Ogden, and Salt Lake
City, as well as the Virgin River in the southwestern portion of Utah,
and one record from southeastern Utah (Hayward et al. 1976, p. 107).
Recently, nesting has been documented at Ouray NWR on the Green River
and the Matheson Wetland Preserve near Moab. Additionally, there are
reports from at least five other areas where breeding has been
suspected (Owens 1998, pp. 3-6). Avian surveys of riparian habitats
within the historical range (the Salt Lake Valley) recorded 3 yellow-
billed cuckoos in 7,000 survey hours (Owens 1998, pp. 3-6). No
statewide systematic surveys for yellow-billed cuckoos have been
conducted. Survey results and the available literature indicate an
extremely small breeding population of yellow-billed cuckoos in Utah.
Therefore, we conclude that the number of breeding pairs in the State
is fewer than 10 and not likely more than 20 pairs.
Nevada
The historical status of the yellow-billed cuckoo in Nevada is
poorly documented, although there is evidence the species nested in
western Nevada along the lower Truckee and Carson Rivers and in
southern Nevada along the Colorado and Virgin Rivers (Linsdale 1951, p.
235; Neel 1999, pp. 118-120).
Surveys using call-playback techniques were completed along the
Truckee, Carson, and Walker Rivers in the early 1970s. In surveys of
the six remaining areas of habitat able to support yellow-billed
cuckoos, as described by Gaines (1974, p. 206), no birds were heard or
seen (Oakleaf 1974, pp. 18-19). Early documentation of yellow-billed
cuckoos nesting in Nevada included a pair at Beaver Dam Wash, Lincoln
County, in 1979 (Neel 1999, p. 119). The only set of persistent
sightings along the Carson River occurred on portions near Lahontan
Reservoir (Neel 1999, pp. 118-120), where sightings of single birds
year after year suggested long-term occupancy from 1986 to 1997
(Tomlinson 2010, p. 1). At least one yellow-billed cuckoo was detected
during surveys at the Lahontan Reservoir delta in 2012 indicating
continued residency at that location (Great Basin Bird Observatory
2013, p. 48). Between 1990 and 1999, Neel (1999, p. 119) reported only
sporadic sightings of single birds throughout the State.
Beginning in 2000, annual survey efforts became more consistent in
the southern portion of the State. The Nevada Division of Wildlife
(NDOW) (2001, pp. 1-8) conducted surveys in 2000 in southern Nevada and
documented 19 yellow-billed cuckoos, comprising 4 pairs and 11 unpaired
birds with no nests found. NDOW surveys in 2000 and 2001 detected more
birds (19 and 28, respectively) than in subsequent years, with a
general decline in detections from 2002 to 2009, although the survey
area was smaller because of reduced access to private lands (Tomlinson
2010, p. 1). Surveys conducted at the Warm Springs Natural Area on the
Muddy River documented a nesting record for the species in 2000, but
also indicated a general decline in bird numbers from 2002 to 2009
(Tomlinson 2010, p. 1). Surveys conducted by the San Bernardino County
Museum at sites along the Virgin and Muddy Rivers between 2000 and 2008
detected yellow-billed cuckoos in all but one year, with the number of
individuals detected ranging from a low of 3 to a high of 12 (Braden et
al. 2009, pp. 1-58). These surveys were resumed by the Southern Sierra
Research Station in 2009 and detected one bird at each of two
locations: Pahranagat Valley and the Key Pittman Wildlife Area
(Tomlinson 2010, p. 2).
Incidental yellow-billed cuckoo detections were also made during
other bird surveys in the Pahranagat Valley in 2008, 2010, and 2012
(SWCA 2013, Table C-1). In 2006, surveys were conducted for the species
at four Nevada sites within the Lower Colorado River Multi-Species
Conservation Plan Boundary area (Johnson et al. 2007, pp. 1-220),
resulting in detection of eight yellow-billed cuckoos (Johnson et al.
2007, pp. 13-16). Fairly extensive surveys of potential habitat at the
Ash Meadows NWR resulted in detection of single yellow-billed cuckoos
in 2008 and 2009 (Tomlinson 2010, p. 2). Additional protocol surveys
were conducted in 2009 and 2010 in southern Nevada along the Muddy and
Virgin Rivers, resulting in the detections of 3 cuckoos at Overton
Wildlife Management Area along the Muddy River and 1 cuckoo detection
at Mormon Mesa along the Virgin River in 2010 (McNeil et al. 2010, pp.
27-29; McNeil et al. 2011, pp. 140-142). In addition, incidental
detections of cuckoos were made almost annually during other bird
surveys along the Virgin and lower Muddy Rivers between 2008 and 2012
with the highest number of 4 cuckoos occurring in 2010 (SWCA 2013,
Table C-1). Survey results and the available literature indicate a
small breeding population of yellow-billed cuckoos in Nevada.
Therefore, we conclude that fewer than 10 breeding pairs occur in the
State.
California
In California prior to the 1930s, the species was widely
distributed in suitable river bottom habitats, and was locally common
(Grinnell and Miller 1944, pp. 186-187; Small 1994, pp. 130-131).
Yellow-billed cuckoos primarily nested in three general areas
[[Page 61637]]
of the State: (1) Coastal counties from San Diego County near the
Mexico border to Sonoma County in the San Francisco Bay region, (2) the
Central Valley from Kern County through Shasta County, and (3) along
the lower Colorado River (Dawson 1923, pp. 2-7; Grinnell and Miller
1944, pp. 186-187; Gaines and Laymon 1984, pp. 53-58; Small 1994, 130-
131). Yellow-billed cuckoos also bred locally elsewhere in the State,
including in Inyo, San Bernardino, and Siskiyou Counties (Grinnell and
Miller 1944, pp. 186-187).
The early ornithological literature for California was summarized
and evaluated by Gaines (1974a, p. 204; 1974b, pp. 2-4), Gaines and
Laymon (1984, pp. 53-58), and Hughes (1999, p. 4). Collectively, they
report 42 locations where the yellow-billed cuckoo was historically
reported or collected in abundance, but is no longer found today.
Laymon and Halterman (1987b, p. 24) estimated that the geographical
range of the yellow-billed cuckoo in California is about 30 percent of
what it was historically. Hughes (1999, p. 2) provides an estimate of
15,000 breeding pairs in California during the late 19th century.
Gaines (1974, p. 208) believed that predevelopment yellow-billed cuckoo
populations in California were even greater than implied by the early
literature, due to the species' inconspicuous behavior and the fact
that large tracts of floodplain riparian habitat had already been lost
to development before the first records and accounts of the species
began appearing in literature. Most modern investigators believe that
the initial decline of the yellow-billed cuckoo population in
California occurred following the major era of development that began
about the mid-1800s (Gaines and Laymon 1984, p. 73; Laymon and
Halterman 1987b, pp. 19-25; Launer et al. 1990, pp. 2-3). The species
was listed by the State of California as threatened in 1971, and was
reclassified as endangered in 1987.
The species' population no longer breeds in the San Joaquin Valley.
Yellow-billed cuckoos historically were recorded from every county in
the San Joaquin Valley region except Kings County, and were locally
common as a breeding bird at least in San Joaquin, Kern, Fresno, and
Stanislaus Counties (Gaines and Laymon 1984, p. 66). The last nesting
record for this region was in 1974 on Lewis Creek near Lindsey, Tulare
County (Laymon and Halterman 1987a, p. 24).
The first statewide survey for yellow-billed cuckoos was conducted
in 1977 and located 121 to 163 pairs of yellow-billed cuckoos during 44
days of survey effort (0.55-0.74 yellow-billed cuckoo pairs per survey
hour)(Gaines and Laymon 1984, p. 77; Halterman et al. 2001, p. 47). The
second statewide survey, conducted in 1986 and 1987 with 124 days of
survey effort, estimated 32 to 42 breeding pairs in the State, a
decline of 66-81 percent from the 1977 survey (0.05-0.07 yellow-billed
cuckoo pairs per survey hour)(Gaines and Laymon 1984, pp. 59-72; Laymon
and Halterman 1987a, p. 7). The third statewide survey, in 1999 and
2000, was conducted over 134 days, and estimated 39 to 43 breeding
pairs (0.06 yellow-billed cuckoo pairs per survey hour), a similar
population level to 1987, but lower than 1977 (Halterman et al. 2001,
p. 47) (Figure 3). The main difference in the most recent statewide
survey (1999 to 2000) when compared to earlier surveys (1977 and 1987)
was the absence of yellow-billed cuckoos at isolated sites in the Prado
Flood Control Basin in Riverside County, the Mojave and Amargosa Rivers
in San Bernardino County, and the Owens Valley in Inyo County where
they had previously bred, indicating a contraction of the range to the
core areas of occurrence along the Sacramento, Kern, and Colorado
Rivers. In all, the California population of the western yellow-billed
cuckoo today is less than 1 percent of its estimated historical
population size.
[GRAPHIC] [TIFF OMITTED] TP03OC13.034
[[Page 61638]]
Yellow-billed cuckoos have been considered accidental in coastal
northern California; however, from 2000 through 2012, surveys and
anecdotal observations along the lower Eel River in Humboldt County
detected yellow-billed cuckoos, and breeding was probable during at
least two of those years (McAllister et al. 2010, pp. 1-6). If nesting
is confirmed, this would document a new breeding site in the State.
Based on statewide survey results, only three areas in the State
support more than a few breeding pairs on a regular basis: (1) The
Sacramento River (roughly between Colusa and Red Bluff), (2) the South
Fork of the Kern River upstream of Lake Isabella, and (3) the lower
Colorado River (Laymon and Halterman 1987a, pp. 1-18). Results of
surveys and population trends for these sites are summarized below.
Sacramento River--Grinnell and Miller (1944, pp. 186-187) listed
the yellow-billed cuckoo as a common to fairly common breeder in the
Sacramento Valley. Gaines and Laymon (1984, pp. 59-60) summarized
historical occurrence in the Sacramento Valley, and cited Cooper (1870,
pp. 371-373) who found the species quite common in the vicinity of
Sacramento in 1865 and Belding (1890, p. 87) who found them common in
the vicinity of Marysville in 1878. Gaines (1974, pp. 204-205)
conducted the first surveys for yellow-billed cuckoos on the Sacramento
River between Red Bluff and Colusa during 1972, and found 28
individuals at 15 sites. The following year (1973) he repeated this
survey, and found 29 yellow-billed cuckoos at 21 sites (40 survey
hours) (Gaines and Laymon 1984, p. 59). During a statewide yellow-
billed cuckoo survey in 1977, researchers found 44 yellow-billed
cuckoos at 29 sites in this same stretch of the Sacramento River, but
with greater survey effort (60 survey hours) (Gaines and Laymon 1984,
pp. 59-62). From these surveys it was estimated that 29 to 60 pairs of
yellow-billed cuckoos nested along the Sacramento River in 1977.
The Sacramento River was resurveyed in 1987, and a much lower
population of 18 to 22 pairs was found despite a more intense survey
effort (128 survey hours) (Laymon and Halterman 1987a, p. 6). Halterman
(1991, p. 24) continued surveys on the river for 3 additional years
with even greater survey effort (255 survey hours each year), and found
breeding populations of 35 pairs, 26 pairs, and 23 pairs in 1988, 1989,
and 1990, respectively. Surveys in 1999 found 28 to 32 pairs of yellow-
billed cuckoos, and surveys in 2000 located 35 to 40 pairs (Halterman
et al. 2001, p. 39). The most recent survey on the Sacramento River,
conducted in 2010, located only 16-18 yellow-billed cuckoos at 48
sites, despite many more hours of surveying effort (1,191 survey hours)
(Dettling and Howell 2011, p. 31).
Yellow-billed cuckoo populations have declined on the Sacramento
River in the past 40 years. In the 1970s a yellow-billed cuckoo was
found about once every 1.4 hours of survey effort. During the 1980s a
yellow-billed cuckoo was found half as often with one every 2.8 hours
of survey effort. From 1990 to 2000 a yellow-billed cuckoo was found
every 2.9 hours of survey effort, but in 2010 it took 66.2 hours of
survey effort to locate a yellow-billed cuckoo (Figure 4). Yellow-
billed cuckoos still occupy this site, but the population has declined
by at least 80 percent over the past 35 years, with a major continuing
decline in the most recent 10 years. Since the extent of habitat has
remained stable or increased, it appears that much of the potential
habitat today is unused.
[GRAPHIC] [TIFF OMITTED] TP03OC13.033
South Fork Kern River--The 3,300-ac (1,335-ha) riparian forest in
the South Fork Kern River Valley is one of the largest remaining
contiguous tracts of riparian habitat in California. This site has been
the most regularly surveyed of any of the yellow-billed cuckoo breeding
locations in California. The species' occurrence at this site was first
documented in 1911 by a specimen collected by Grinnell's Mount Whitney
Expedition (MVZ Birds 19836, Museum of Vertebrate Zoology,
University of California (UC) Berkeley). Gaines (Gaines and Laymon
1984, p. 64) rediscovered this population, finding nine individual
yellow-billed cuckoos there during his 1977 statewide survey of the
species. From 1985 through 2001 this population was intensively
monitored, and the number of pairs and
[[Page 61639]]
most nests found each year were documented (Laymon and Williams 2001, p
4; Laymon and Williams 2002, p. 5). During this period, the population
fluctuated from a low of 2 pairs in 1990 to a high of 24 pairs in 1992,
with a yearly average of 10.6 pairs.
From 2002 to 2004 and 2008 to 2010, the population was surveyed
less intensively and fewer nests found (Halterman 2003, p. 10;
Halterman 2004, p. 10; Henneman 2008, pp. 8-10; Henneman 2010, pp. 8-
10; Whitfield and Stanek 2011, pp. 8-10). The number of yellow-billed
cuckoo pairs is no longer being estimated, but from reviewing the
location of the survey sightings, approximately 8 to 14 pairs (with an
average of 10.5 pairs) have nested in the area during this period. From
the available survey data and literature, this small breeding
population currently appears to be stable. Most of the population is
currently nesting on the U.S. Army Corps of Engineers (USACE), U.S.
Forest Service (USFS) South Fork Wildlife Area in the western third of
the site. The eastern two-thirds of the site is sparsely occupied, and
it appears that not all of the potential nesting habitat is currently
being used (Henneman 2008, pp. 8-10; Henneman 2010, pp. 8-10; Whitfield
and Stanek 2011).
Lower Colorado River--The lower Colorado River on the California-
Arizona border supported an estimated 180 yellow-billed cuckoo pairs
during the first California statewide yellow-billed cuckoo survey in
1976 to 1977 (Gaines and Laymon 1984, p. 72). When the second
California statewide survey was conducted in 1986 yellow-billed cuckoos
had decreased by 80-90 percent (Laymon and Halterman 1987a, pp. 34-35).
Another study (Rosenberg et al. 1991, p. 203) estimated a decline of 93
percent over this same time period, from an estimated initial 242 pairs
in 1976 to 1977. Final results from a Service-funded 1999 statewide
survey found only two pairs of yellow-billed cuckoos on the California
side of the Colorado River (Halterman et al. 2001, p. 19), an area
where 44 yellow-billed cuckoos were found in 1977 (Gaines and Laymon
1984, pp. 64-65).
In 2006, surveys were conducted at various sites throughout the
Lower Colorado River Multi-Species Conservation Plan Boundary area for
the yellow-billed cuckoo (Johnson et al. 2007, pp. 1-220). Two survey
areas were on the California side of the lower Colorado River, the
Picacho State Recreation Area and the Imperial NWR (Imperial Paradise
area); only one bird was detected, at the Picacho State Recreation
Area, Imperial County (Johnson et al. 2007, p. 25). During 2010 and
2011, yellow-billed cuckoos were found at two locations on the
California side of the river. One pair was found at the Picacho State
Recreation Area in both years. At the newly created restoration habitat
at Palo Verde Ecological Reserve, Riverside County, two to five pairs
were found in 2010, and 10 to 19 pairs were found in 2011 (McNeil et
al. 2011, p. 19; McNeil et al. 2012, p. 24). Yellow-billed cuckoo
numbers on the lower Colorado River went from the largest known range-
wide population in 1977 to near extirpation from the region in the
1980s. Recent population increases appear to be a result of increased
habitat from active riparian habitat restoration along the river,
though numbers are still well below 1977 population levels.
Yellow-billed cuckoos have declined by more than 99 percent from
historical levels in California, and declines appear to be continuing,
especially along the Sacramento River and at isolated sites that
recently supported small populations, but are now unoccupied. Current
nesting populations for the State are found at only 3 locations, and
likely do not exceed 40 to 50 pairs, down from approximately 280 pairs
as recently as 1977 and perhaps as many as 15,000 pairs prior to the
increased human settlement in the 1850s.
Arizona
The yellow-billed cuckoo was historically widespread and locally
common in Arizona (Phillips et al. 1964, p. 45; Groschupf 1987, p. 7).
A 1976 study based on existing habitat and known yellow-billed cuckoo
population densities estimated 846 pairs were present on the lower
Colorado River and its five major tributaries in Arizona (Groschupf
1987, pp. 20-28). In a statewide survey in 1999 that covered 265 mi
(426 km) of river and creek bottoms, 172 yellow-billed cuckoo pairs and
81 single birds were located in Arizona (Corman and Magill 2000, pp. 9-
10). While this survey did not cover all potential yellow-billed cuckoo
habitat in Arizona, it indicated that the number of yellow-billed
cuckoos in 1999 was substantially lower than previous estimates for the
State. However, Arizona still contains the largest remaining yellow-
billed cuckoo population among the States west of the Rocky Mountains,
and the species is considered a Species of Concern by the Arizona Game
and Fish Department, a designation that does not provide protection to
the species (Corman 1999, p. 1). As habitat has declined, yellow-billed
cuckoo numbers have likely declined, as has been documented for the
lower Colorado River (Rosenberg et al. 1991, pp. 202-205) and described
above for California.
Yellow-billed cuckoo populations greater than 10 pairs are found at
12 locations in Arizona: Bill Williams River, Colorado River, Gila
River, Hassayampa River, San Pedro River, Santa Maria River, Verde
River, Sonoita Creek, Santa Cruz River, Upper Cienega Creek, Altar
Valley, and Agua Fria River. Sites with smaller populations are found
at the Roosevelt Lake Complex, Upper Tonto Creek, Pinto Creek, Sycamore
Creek in Pajarita Mountains, Oak Creek, Lower Cienega Creek, Babocomari
River, Pinal Creek, Bonita Creek, San Bernardino NWR, Hooker Hot
Springs, Big Sandy River, and many smaller drainages. However, many
drainages have not been thoroughly surveyed, and it is likely that some
additional yellow-billed cuckoo locations will be discovered. These
include, but are not limited to the mountain ranges of southeastern
Arizona, Eagle Creek, and along the Gila, San Francisco, and Blue
Rivers.
Yellow-billed cuckoo sightings reported by birders between 15 June
and 31 August, 1998 to 2012, in more than 1 year in southeastern
Arizona mountain ranges include Carr Canyon, Ash Canyon, Garden Canyon,
Ramsey Canyon, and Miller Canyon in the Huachuca Mountains; Walker
Canyon, Madera Canyon, and Montosa Canyon in the Santa Rita Mountains;
Scotia Canyon and Sycamore Canyon in the Atascosa/Pajarito Mountains;
French Joe Canyon in the Whetstone Mountains; Harshaw Canyon and
Paymaster Spring in the Patagonia Mountains; Kitt Peak on Baboquivari
Mountain; and a few locations in the Chiricahua Mountains (Bird05
listserve, 2012). Yellow-billed cuckoos are breeding in at least some
of these locations, with nesting confirmed at Sycamore Canyon (Arizona
Game and Fish Department, unpublished data). The Arizona Breeding Bird
Atlas recorded yellow-billed cuckoos on 50 of 1,834 blocks (2.7
percent), illustrating the species' rare status. Yellow-billed cuckoos
were confirmed breeding and probably breeding on 29 of these blocks,
and possibly on 21 blocks (Corman and Wise-Gervais 2005, pp. 202-203).
Multiyear surveys have been conducted at five of these locations, which
are discussed below.
Bill Williams River--In the mid-1970s, an estimated 57 pairs of
yellow-billed cuckoos bred in the riparian forest of the Bill Williams
River Delta (Gaines and Laymon 1984, p. 71). Following the sustained
high water levels of 1983 to 1984 and 1986, which inundated and killed
most of the
[[Page 61640]]
cottonwoods and willows along the Colorado River, yellow-billed cuckoo
numbers also declined on the Bill Williams River Delta where similar
habitat mortality occurred (Rosenberg et al. 1991, p. 203). In 1987, 17
pairs of yellow-billed cuckoos were located at this site and a total of
25 to 30 pairs were estimated to be present, a decline of 47 to 56
percent over 10 years (Laymon and Halterman 1987a, p. 32). Surveys were
conducted regularly at this site from 1993 to 2002. The breeding
population fluctuated from a low of 6 to 9 pairs in 1999 and 8 pairs in
2002 to a high of 28 to 30 pairs in 1993 and 28 to 39 pairs in 2001
(Halterman 2003, p. 32). Surveys were next conducted at this site in
2006 using revised survey protocols; 117 detections were recorded and
no attempt was made to estimate the number of pairs occupying the site.
In 2007, researchers recorded 139 detections at this site, and no
estimate of pairs was made (Johnson et al. 2008a, p. 29). In 2010,
researchers estimated 12 to 31 pairs, and the most recent survey in
2011 estimated 9 to 23 pairs (McNeil et al. 2010, p. 19; McNeil et al.
2012, p. 24). Bill Williams River NWR is considered the largest,
highest quality stand of suitable habitat for the yellow-billed cuckoo
along the lower Colorado River (Johnson et al. 2008a, p. 106). Data
from this site show an important, but fluctuating, breeding population
that has not recovered to 1977 levels.
Lower Colorado River--The lower Colorado River on the California-
Arizona border supported an estimated 180 yellow-billed cuckoo pairs in
1976 to 1977 (Gaines and Laymon 1984, p. 72), a number that had
declined by an estimated 80-90 percent in 1986 (Laymon and Halterman
1987a, pp. 34-35). In 2006 and 2007, surveys were conducted at various
sites throughout the Lower Colorado River Multi-Species Conservation
Plan Boundary area for the yellow-billed cuckoo (Johnson et al. 2007,
pp. 1-220; Johnson et al. 2008a p. 1). Breeding was detected at the
Grand Canyon National Park/Lake Mead National Recreation Area in 2006
(Johnson et al. 2008a, p. 1107). In addition to the Bill Williams River
NWR, other sites in Arizona where Johnson et al. (2008a, p. 29)
detected yellow-billed cuckoos in 2006 and 2007 include: the Grand
Canyon National Park/Lake Mead National Recreation Area, Havasu NWR,
Cibola NWR, Imperial NWR, Gila-Colorado River confluence, Limitrophe
Division, and Quigely Pond Wildlife Management Area (Johnson et al.
2008a p. 107). In 2010, based on intensive surveys, 8 to 18 pairs were
estimated, and the most recent survey in 2011 estimated 9 to 23 pairs
on the Arizona side of the Colorado River, excluding the Bill Williams
River (McNeil et al. 2010, p. 19; McNeil et al. 2012, p. 24). Recent
population estimates are well below the breeding population in 1977,
even though more area was surveyed.
Upper San Pedro River--This site has had the largest yellow-billed
cuckoo population in Arizona. Yellow-billed cuckoos were surveyed on 42
mi (67 km) of riparian habitat on the upper San Pedro River for 7 years
from 2001 to 2007 (Halterman 2002, pp. 10, 22; Halterman 2003, pp. 9,
23; Halterman 2004, pp. 9, 33-34; Halterman 2005, pp. 8, 22-23;
Halterman 2006, pp. 26-27; Halterman 2007, pp. 5, 11; Halterman 2009,
p.23). The number of surveys varied from year-to-year with one to five
surveys per year and with different methods used to determine
population size. In 2001, researchers estimated a total of 40 to 52
pairs, and 29 to 50 pairs the next year. A total of 26 or more pairs
was estimated in 2003, but the number of pairs was not estimated after
that year. Year-to-year comparisons were made by summing the maximum
number of yellow-billed cuckoos in each transect for each year, which
yields a minimum population of individual yellow-billed cuckoos over
the breeding season.
In 2001, reserchers located 71 individual yellow-billed cuckoos.
The population rose to 114 individual yellow-billed cuckoos in 2002 and
128 individual yellow-billed cuckoos in 2003, before dropping to 101
yellow-billed cuckoos in 2004, 76 in 2005, and a low of 47 in 2006. In
2007, the number of yellow-billed cuckoos detected increased to 83. The
2006 results indicated a continuing downward trend, but the 2007
results show a substantial increase in the population. Other yellow-
billed cuckoo populations have shown annual fluctuation in detections
(Halterman 2007, p. 23). Unfortunately, intensive yellow-billed cuckoo
surveys have not been conducted at this site since 2007, so it is
uncertain whether or not the population has truly rebounded from the
2006 low. During 2001 and 2002, researchers detected 36 and 81 yellow-
billed cuckoos, respectively, along the San Pedro River during
southwestern willow flycatcher surveys (EEC 2002, pp. 6, 12, 13). A
repeat of these surveys in 2009 detected only 26 yellow-billed cuckoos
(The Vernadero Group 2009, pp. 9, 19). While survey effort between
these two time periods may not be comparable, the findings show
evidence of a long-term downward trend for yellow-billed cuckoos at
this location.
Sonoita Creek--A 4-mi (6-km) segment of Sonoita Creek was surveyed
in 7 years between 1976 and 1986 (Groschupf 1987, p. 14). Yellow-billed
cuckoo pairs were not estimated, but lows of 5 and 6 individuals were
found in 1976 and 1986, respectively, and highs of 24 to 28 individuals
were found between 1977 and 1979. The site was surveyed again in 1998
and 1999, with 11 to 12 pairs and 8 to 9 single yellow-billed cuckoos
located (Corman and Magill 2000, pp. 39-40). In 2005, 17 individuals
were found while conducting bird surveys for Important Bird Area
designation (Arizona Audubon 2012, http://iba.audubon.org/iba). This
population, while fluctuating, does not appear to have decreased in
size from 1976 to 2005. No recent yellow-billed cuckoo surveys have
been conducted at this site.
Verde River--Surveys conducted in 2004 and 2005 at 37 sites within
the Verde River watershed were done at historical sites (16) at
locations where yellow-billed cuckoos were previously detected in 1998
to 1999 and at random sites (21) with riparian forest that appeared to
be suitable nesting habitat (Holmes et al. 2008, pp. 6-7). In the 2
years, 59 percent of sites had detections: 75 percent of historical
sites and 48 percent of random sites (Holmes et al. 2008, p. v). Holmes
et al. (2008, p. 20) confirmed nesting at five sites and found evidence
of probable breeding at nine additional sites. The maximum number of
detections during any one survey period was 23 in 2004 and 31 in 2005.
Thus, the available literature and surveys suggest that yellow-
billed cuckoo populations in Arizona over the past 30 years have
declined by 70 to 80 percent, with recent declines since approximately
2000 at some of largest populations (for example, San Pedro River). At
present, it appears that the State's population could be as low as 170
pairs of yellow-billed cuckoos, and probably does not exceed 250 pairs.
Despite these recent declines, the population of the western yellow-
billed cuckoo in Arizona is the largest in the United States.
Western New Mexico
Yellow-billed cuckoos were historically common in riparian areas
along the Rio Grande, as well as uncommon to common locally along
portions of the Gila, San Francisco, and San Juan Rivers (Bailey 1928,
pp. 307-309; Hubbard 1978, p. 32). A habitat analysis and wildlife
survey of the middle Rio Grande Valley from
[[Page 61641]]
Espanola to La Joya estimated that 315 pairs of yellow-billed cuckoos
bred along this river segment (Howe 1986, p. 10).
Recent surveys have been conducted by the Bureau of Reclamation
(Reclamation) from 2006 through 2010 along the middle Rio Grande, from
Highway 60 downstream to Elephant Butte Reservoir (Ahlers et al. 2010,
p. 4; Ahlers and Moore 2011, p. 13). The area covered by the surveys
increased from 36 mi (58 km) in 2006 to 90 mi (144 km) in 2009 and
2010. Data indicate detection of an estimated 44 pairs in 2006, 71 in
2007, 87 in 2008, 95 in 2009, and 75 in 2010; however, these estimates
are not directly comparable due to variation in survey efforts and
protocols (Ahlers et al. 2010, pp. i, 3, 12, 17). These surveys have
documented a sizable population, but many fewer than the 315 pairs
estimated for this region in 1984 (Howe 1986, p. 10).
Systematic surveys have not been carried out on the Gila, San
Francisco, and San Juan Rivers. The extent of habitat in these areas is
limited, and much is discontinuous and fragmented. Based on available
habitat, a maximum of 35 yellow-billed cuckoo pairs could breed on the
Gila River, while no more than 15 and 5 pairs could breed on the San
Juan and San Francisco Rivers, respectively. An estimated 100 to 155
yellow-billed cuckoo pairs currently breed in western New Mexico.
Western Texas
The yellow-billed cuckoo historically was considered to be fairly
common in riparian habitat at elevations of 3,000-7,500 ft (900-2,200
m) in El Paso, Hudspeth, Culberson, and Presidio Counties (Oberholser
and Kincaid 1974, pp. 434-435; Rappole and Blacklock 1994, pp. 125-
126). Recent information reports that yellow-billed cuckoos have
declined in El Paso County (Peterson and Zimmer, 1998, p. 66).
Population reports in the Trans-Pecos area of western Texas near Big
Bend National Park show scattered populations of yellow-billed cuckoos
(Wauer 1971, pp. 18, 27). These populations tend to be associated with
areas of springs and developed wells or earthen ponds that support
cottonwoods and willows.
Yellow-billed cuckoo population trends from 1966 to 1998 for the
entire State of Texas, eastern and western, show a decline (USGS
Biological Resources Division 1999, p. 1). The Texas Parks and Wildlife
Department (TPWD) currently does not separate the eastern and western
populations of the yellow-billed cuckoo, and identifies the species as
globally abundant and State secure since the State ranking was last
revised in 1994. However, subsequent publications by the TPWD indicate
the species is becoming increasingly rare and declining (Shackelford
and Lockwood 2000, p. 1). During 4 years, between 1988 and 1998, a 116-
mi (189-km) segment of the Rio Grande (16 mi (26 km) in New Mexico and
99 mi (159 km) in Texas) was surveyed for yellow-billed cuckoos. The
1988 and 1992 survey results were similar, with yellow-billed cuckoos
responding at 20 of 67 sites and 25 of 109 sites, respectively. The
population then dramatically declined, with only 4 yellow-billed
cuckoos at 113 sites in 1995 and 7 yellow-billed cuckoos at 134 sites
in 1998 (Sproul 2000, p. 3). The author concluded that the yellow-
billed cuckoo is a rare, highly vulnerable, and declining species in
the Rio Grande Valley of southern New Mexico and extreme west Texas
(Sproul 2000, p. 5). Sproul attributed the decline to habitat loss and
degradation as well as other unknown factors in the species' migratory
and wintering grounds (Sproul 2000, pp. 3-4). The current population of
the western yellow-billed cuckoo in western Texas is likely fewer than
10 pairs.
Northwestern Mexico
The yellow-billed cuckoo breeds locally in northwestern Mexico, and
is a widespread transient during migration (Howell and Webb 1995, pp.
346-347). In northwestern Mexico, it has been recorded as a summer
resident (presumably breeding), including the extreme northern and
southern portions of the Baja California Peninsula, northwest Mexico
from Sonora and Chihuahua south to western Durango and Sinaloa (Howell
and Webb 1995, pp. 346-347), and irregularly and locally south to
western Nayarit and western Zacatecas (World Bird Info 2012).
Baja California Peninsula--Historically, the yellow-billed cuckoo
was a rare and local migrant and summer resident in Baja California and
Baja California Sur (Grinnell 1928, p. 119). Miller (1950, p. 83)
observed a migrating flock of yellow-billed cuckoos in the Cape region
of Baja California Sur in late May or early June 1896. Lamb (1927, p.
157), during 2 years living in the Cape region, saw yellow-billed
cuckoos on only two occasions, once in late June and again in early
September. A recent status review of birds on the Baja California
Peninsula listed the species as a probable breeder only along the
Colorado River and in the Cape region (Howell 2001, p. 17; Howell et
al. 2001, p. 182). The population along the Colorado River was formerly
numerous, but now very few yellow-billed cuckoos can be found (Patten
et al. 2001, p. 46). Bird surveys conducted along the Colorado River,
Mexico, from May 2002 to July 2003 concluded that the presence and
density of breeding yellow-billed cuckoos is largely dependent on the
state of riparian habitat and presence of water (Hinojosa-Huerta et al.
2008, pp. 75-92). Suitable habitat disappeared from the R[iacute]o
Colorado floodplain in the latter part of the 20th century due to
dewatering of this portion of the river. Pulse floods in the 1990s and
2000s promoting cottonwood and willow habitat regeneration resulted in
yellow-billed cuckoos returning to breed once riparian nesting habitat
developed. Yellow-billed cuckoo persistence will depend on dedicated
instream flows and pulse floods, maintenance of vegetative cover and
structural diversity, and an increase in older riparian stands
(Hinojosa-Huerta et al. 2008, pp. 75-92). The population levels of
yellow-billed cuckoos in the Cape Region of Baja California Sur are not
known, but from available information they appear to be extremely small
and may not exceed 10 breeding pairs.
Sonora--Yellow-billed cuckoos are a common summer resident in
Sonora, and were observed with higher frequency than in adjacent
Arizona (Russell and Monson 1998, p. 131). In the vicinity of Alamos in
southern Sonora, Short (1974, p. 24) found the species a common to
abundant breeder during the rainy season in late July and early August.
During general bird surveys in northern Sonora from 2000 to 2007,
yellow-billed cuckoos were detected in 11 of 16 watersheds (Flesch
2008, pp. 35-36). On the Sonoyta River in northwestern Sonora, the
species was not found on the lower stretches and was rare upstream on
the Vamori section. On Rio de la Concepcion, yellow-billed cuckoos were
not found on the lower river section or the upper or lower Plomo
sections. They were rare on the upper and lower Sasabe sections and
uncommon on the Altar, Busani, Coyotillo Magdalena, and Cocospera-
Bambuto sections. They were not found on the Santa Cruz River and were
uncommon on the San Pedro River. They were also uncommon on the San
Miguel and Bacanuchi-Sonora section of the Rio Sonora. The author
defined rare as ``present but rarely detected and often restricted to
localized area'' and defined uncommon as ``present but may not be found
in a day or two of field observations'' (Flesch 2008, pp. 35-36).
Yellow-billed cuckoos were described as fairly common summer
residents, probable breeders, on bird transect
[[Page 61642]]
surveys conducted in July and September 2007 and July 2008 between
1,542-3,773 ft (470-1150 m) in the 45,000-ac (18,211-ha) Northern
Jaguar Reserve in the foothills of the Sierra Madre near the town of
Sahuaripa in east-central Sonora (Flesch 2009, pp. 5, 9, 12, 16, 21).
The reserve, bordered by the R[iacute]os Aros and Bavispe, is composed
of oak forests mixed with native fan palms, dense thornscrub that
transitions into subtropical vegetation, mesquite bosque, and perennial
streams lined with sycamores.
Breeding yellow-billed cuckoos were documented from July through
September along approximately 60 km (37 mi) of the Santa Cruz River in
northern Sonora during riparian bird point count surveys in 2001 and
2003. They were fairly common at sites ranging from typical cottonwood-
dominated riparian habitat (with or without understory) to mesquite-
oak-grass habitat. The riparian habitat in this region is moderately
impacted from water use, vegetation loss, presence of cattle, and land
clearing for agriculture (Sonoran Institute 2008; pp. 2, 25, 55).
Yellow-billed cuckoo call playback surveys conducted from 21 June
through 26 September 2003 documented 142 yellow-billed cuckoos at 10
sites ranging from 1,148 ft to 3,937 ft (350 to 1,200 m). Yellow-billed
cuckoos were found in riparian habitat at Agua Calienta on the
R[iacute]o Bambuto north of Imuris; R[iacute]o Tubutama near Tubutama
and La Reforma; R[iacute]o Cuchujaqui northwest of Alamos; R[iacute]o
Sonora at Aconchi and Baviacora, northeast of Hermosillo on the
Cananea-Ures stretch of State Highway 116; El Gavilan on R[iacute]o
Sonora east of Ures; Upper R[iacute]o San Pedro near San Pedro
Palominas, and near the ejido Jose Ma. Morelos in Cananea (IMADES 2003,
pp. 4, 14, 20).
Yellow-billed cuckoo call playback surveys conducted from July
through September 2005 documented yellow-billed cuckoos in northeastern
Sonora along the R[iacute]os Sonora, Bacanuchi, Cajon Bonito, Bavispe,
Moctezuma, and Sahuaripa. Habitat consisted of cottonwood, willow, and
mesquite (CEDES 2005, pp. 5, 10, 11). Extensive grazing, agriculture,
mining and related water withdrawals have reduced the riparian quality
on these rivers.
Marshall (1957, p. 74), in his pine-oak woodland bird study in
southern Arizona and adjacent Mexico, found the yellow-billed cuckoo as
a migrant or wanderer in riparian timber only once in Sonora in the
Ajos Mountains on July 17, 1952. During wildlife surveys by boat and
foot in July and August 2005, of the 115-mi (185-km) stretch of the
R[iacute]os Aros and Yaqui and tributaries from N[aacute]tora (2,275 ft
(700 m)) to El R[iacute]o (1,138 ft (350 m)) in east-central Sonora,
yellow-billed cuckoos were described as common in riparian groves and
thorn scrub woodland. They were detected on both side drainages and
main river channels (O'Brien et al. 2006, pp. 4, 8, 24, 37, 46, 51).
In a study focusing on cactus ferruginous pygmy-owls during late
spring and summer from 2001 through 2010, Flesch (2012 in litt.) found
yellow-billed cuckoos at 95 sites from June to September at elevations
from 328 to 6,902 ft (100 to 2,104 m). The number of birds at each site
ranged from 1 to 15 individuals. Flesch also confirmed breeding at four
sites in thorn scrub habitats and at one site in upland Sonoran Desert
habitat. These records indicate a broader use of habitat by yellow-
billed cuckoos in Sonora. Yellow-billed cuckoos are more common as
breeders in southern Sonora where they nest in thorn forest than in the
more arid northern Sonora. There is some evidence that yellow-billed
cuckoos may be nesting farther north and then re-nest in southern
Sonora and northern Sinaloa during the rainy season in late July and
August (Rohwer et al. 2009, pp. 19050-19055), but additional data are
needed to confirm where and how commonly this occurs. Yellow-billed
cuckoos appear to breed at higher density, especially in southern
Sonora, but the breeding population for the State of Sonora is probably
similar to the State of Arizona with 150 to 250 pairs because Sonora is
half the size of Arizona. However, some of the yellow-billed cuckoos
that breed in southern Sonora late in the nesting season may have been
counted on breeding grounds farther north earlier the same year.
Chihuahua--Most of the State of Chihuahua is desert with very
little rainfall and few waterways with significant riparian habitat.
The Rio Conchos is the primary river system that drains the southern
half of the State. This river is highly degraded, with a high density
of nonnative tamarisk and little regeneration of willows and
cottonwoods due to extremely heavy grazing. This problem has been
worsened by a prolonged drought from the late 1990s to the present.
Only one sighting of a yellow-billed cuckoo is listed on the e-Bird
online database for the State of Chihuahua, found on July 1, 2003,
along Highway 16 between the city of Chihuahua and the town of Lopez
Mateos (Cornell Lab of Ornithology 2012). The breeding population for
the State of Chihuahua is likely very low, probably in the low double
digits and possibly in the single digits.
Sinaloa--How far south yellow-billed cuckoos breed in Sinaloa is
uncertain. The only two observations of the species (Cornell Lab of
Ornithology 2012) are from extreme northern Sinaloa along the Rio
Fuerte. Because a thorough survey has not been conducted, the yellow-
billed cuckoo population in the State is likely higher than these
records imply. However, much of the thorn forest and riparian habitat
has been converted to industrial agriculture over the past 30 years
(Rohwer 2010, p. E16). The breeding population of yellow-billed cuckoos
in Sinaloa is unlikely to exceed that of Sonora (150 to 250 breeding
pairs), and it may be less.
Western Durango--Three observations of the yellow-billed cuckoo
(Cornell Lab of Ornithology 2012) have been made for the State of
Durango west of the Continental Divide. The population for this region
is likely very low, possibly in the low double or single digits.
Population summary in Mexico--The available literature indicates
that knowledge about the status of the breeding population of the
western yellow-billed cuckoo in Mexico is less certain than in the
United States. No systematic State-level surveys for the species have
been carried out in any of the Mexican States. General bird surveys in
Sonora have found yellow-billed cuckoos in similar habitats and
abundances as in Arizona, as well as in thorn forest and dry deciduous
forest, which do not occur north of Mexico. The riparian habitat in
Mexico appears to be more fragmented and heavily grazed than it is
north of the international border, and the thorn-forest habitat that
the species is using in southern Sonora and Sinaloa is being converted
to industrial agriculture at a high rate. Therefore, we conclude that
the western yellow-billed cuckoo in Mexico has a breeding population of
330 to 530 pairs that is likely declining.
Population Summary of the Western Yellow-billed Cuckoo--The
available surveys and literature support the conclusion that the
population of the western yellow-billed cuckoo has declined by several
orders of magnitude over the past 100 years, and that this decline is
continuing. Recent declines over the past 15 years have shown both a
loss of breeding yellow-billed cuckoos in smaller isolated sites and
declines in numbers at core breeding areas. The current breeding
population is low, with 350 to 495 pairs north of the Mexican border
and another 330 to 530 pairs in Mexico for a total of 680 to 1,025
breeding pairs. The breeding population may actually be lower than
these estimates, as some of these pairs may be counted twice since
yellow-billed
[[Page 61643]]
cuckoos apparently move into southern Sonora and Sinaloa during the
rainy season in late July and August after they have previously bred
farther north. Therefore, we conclude that the western yellow-billed
cuckoo has a small and declining population.
Summary of Factors Affecting the Species
Section 4 of the Act, and its implementing regulations at 50 CFR
part 424, set forth the procedures for adding species to the Federal
Lists of Endangered and Threatened Wildlife and Plants. Under section
4(a)(1) of the Act, we may list a species based on any of the following
five factors: (A) The present or threatened destruction, modification,
or curtailment of its habitat or range; (B) overutilization for
commercial, recreational, scientific, or educational purposes; (C)
disease or predation; (D) the inadequacy of existing regulatory
mechanisms; and (E) other natural or manmade factors affecting its
continued existence. Listing actions may be warranted based on any of
the above threat factors, singly or in combination. Each of these
factors is discussed below.
Factor A. The Present or Threatened Destruction, Modification, or
Curtailment of Its Habitat or Range
The decline of the western yellow-billed cuckoo is primarily the
result of riparian habitat loss and degradation. Within the three
States with the highest historical number of yellow-billed cuckoo
pairs, past riparian habitat losses are estimated to be about 90 to 95
percent in Arizona, 90 percent in New Mexico, and 90 to 99 percent in
California (Ohmart 1994, pp. 276-281; U.S. Department of Interior 1994,
p. 215; Noss et al. 1995, pp. 37, 46; Greco 2008, p. 5). Many of these
habitat losses occurred historically, and although habitat destruction
continues, many past impacts have subsequent ramifications that are
ongoing and are affecting the size, extent, and quality of riparian
vegetation within the range of the western yellow-billed cuckoo. These
ongoing impacts are occurring now and are anticipated to continue for
decades to come.
Moreover, these impacts are often subtle. As described in the
Habitat Use and Needs section, above, during the breeding season, the
habitat of the western yellow-billed cuckoo consists of expansive
blocks of riparian vegetation containing trees of various ages,
including in particular larger, more mature trees used for nesting and
foraging. In order for these areas to remain as viable yellow-billed
cuckoo habitat, the dynamic transitional process of vegetation
recruitment and maturity must be maintained. Without such a process of
ongoing recruitment, habitat becomes degraded and is eventually lost.
In our discussion below, we identify the manmade impacts to riparian
vegetation as resulting in current and ongoing destruction and
modification of existing and future potential habitat for the western
yellow-billed cuckoo.
Additional subtle consequences from the manmade impacts are the
indirect effects that result in the curtailment of the habitat of the
western yellow-billed cuckoo. Past actions by humans have resulted in
changes to the landscape, the hydrology, or both such that they prevent
the riparian plants that are the basis of the species' habitat from
growing at all. The consequences of these past actions may have
initially resulted in destruction or modification of then-existing
riparian habitat; however, once that habitat is lost, the changed
conditions (such as changed hydrologic regime) also prevents riparian
habitat from regenerating, even in the absence of other impacts. For
example, channelization--through manmade levees or other constructs, or
through channel incising as a consequence of other actions--may leave
the geographical area where riparian plants once grew (such as the
watercourse's floodplain) physically untouched, but the altered
hydrology prevents riparian plant species from germinating and growing.
Principal causes of riparian habitat destruction, modification, and
degradation in the range of the western yellow-billed cuckoo has
occurred from alteration of hydrology due to dams, water diversions,
management of riverflow that differs from natural hydrological
patterns, channelization, and levees and other forms of bank
stabilization that encroach into the floodplain. These losses are
further exacerbated by conversion of floodplains for agricultural uses,
such as crops and livestock grazing. In combination with altered
hydrology, these threats promote the conversion of existing primarily
native habitats to monotypic stands of nonnative vegetation, which
reduce the suitability of riparian habitat for the western yellow-
billed cuckoo. Other threats to riparian habitat include long-term
drought and climate change. These threats are summarized in a recent
detailed review of the literature on the subject (Poff et al. 2011).
These Factor A threats are described in more detail below. Moreover,
past and ongoing impacts to the species' habitat are working in
combination with other threats, which are discussed in greater detail
in Factors C and E, below.
Habitat Loss From Dams and Alteration of Hydrology
Dams
Poff et al. (1997, pp. 769-784), Greco (1999, pp. 36-38), National
Academy of Sciences (NAS) (2002, pp. 145-150), and the Service (2002,
Appendix I, pp. 1-12) reviewed the following effects of human
modification of natural hydrological processes on riparian habitat,
including those from dams. Dams result in an immediate effect of
destroying riparian structure and functioning due to habitat
displacement from dam construction and by permanent inundation,
sometimes flooding miles of upstream riparian areas. This results in
the physical loss of riparian vegetation. In the absence of vegetation,
the yellow-billed cuckoo cannot breed, feed, or find shelter. Current
and future releases of water downstream from dams at unnatural rates of
flow, inappropriate times of year, or at too frequent or too infrequent
intervals, may lead to flooding or desiccation beyond the tolerance
limits of the native riparian vegetation, thus resulting in loss of
habitat of the western yellow-billed cuckoo.
Dam construction has been occurring since the settlement of western
North America with its peak in the mid-20th century. These include most
major western rivers, many of which have a series of dams, and include,
but are not limited to, the Sacramento, Kern, San Joaquin, Mojave,
Snake, Gila, Salt, Verde, and Rio Grande, including 25 major reservoirs
built on the Colorado and Green Rivers alone between the 1930s and
1970s (Richter et al. 1998, p. 332). In northern Mexico, some of these
rivers include the R[iacute]o Conchos, Yaqui, and Mayo, R[iacute]o
Bambuto, R[iacute]o Bravo, Tubutama, La Reforma, Cuchujaqui River in
Alamos, Aconchi and Baviacora in R[iacute]o Sonora, and Upper San Pedro
River in Sonora, Mexico (Instituto del Media Ambiente y el Desarrollo
Sustentable del Estado de Sonora (IMADES) 2003, p. 4; Kelly and Arias
Rojo 2007, pp. 2-3; Cornell et al. 2008, p. 96).
There are now dozens of large dams and scores of smaller dams on
rivers throughout the range of the western yellow-billed cuckoo. Today
the rate of building new dams has slowed because most of the highest
quality dam sites already have dams constructed on them. There were
proposals to build two dams on Cottonwood Creek, one of the major
tributaries of the Sacramento River
[[Page 61644]]
(USACE 1982), but it is not clear when or if these dams will be built.
A larger current threat is the enlargement of existing dams.
Enlargement of Terminus Dam on the Tule River in California by 21 ft
(6.5 m) in height was completed in 2004 (Barcouda et al. 2006, p. 12),
and proposals to enlarge Shasta Dam on the Sacramento River by up to
200 ft (62 m) in height and doubling its storage capacity (Reclamation
1999, pp. 3-8) and Friant Dam on the San Joaquin River by up to 140 ft
(43 m) in height are being explored (Reclamation 2003, pp. 3.1-3.8).
Larger dams with additional storage would likely flood potential
western yellow-billed cuckoo habitat upstream and cause additional
hydrologic disruption downstream.
While the amount of habitat lost within the construction zone of a
dam is relatively small, far greater amounts of habitat are destroyed
in the areas of inundation and through the ongoing effects of the
amount and timing of water releases through the dam operation, which
affects both upstream and downstream habitats. Ongoing downstream
effects to riparian habitat from dams include changes in sediment
transport due to sediment retention behind the dams so that channels
below a dam become increasingly ``sediment starved.'' This situation
causes vertical erosion (downcutting), which can lead to loss of river
terraces that sustain riparian vegetation (NAS 2002, pp. 145-150; Poff
et al. 2009, pp. 773-774).
Ongoing operations of large dams can also dampen the magnitude of
normal high flows, thus preventing cottonwood germination (Howe and
Knopf 1991, p. 218), and dewater downstream reaches, causing
substantial declines of riparian forests (NAS 2002, pp. 145-150). For
example, Groschupf (1987, p. 19) found that almost all cottonwoods and
over half of all willow trees were eliminated from one waterway in
Arizona that was exposed to repeated large releases of water from a
dam. This situation reduced the density of yellow-billed cuckoos from
13 per 100 ac (40 ha) before the flooding to 3 per 100 ac (40 ha) after
the flooding (Groschupf 1987, p. 19). In another example, a study of
the San Joaquin River from downstream of the Friant Dam to the Merced
River confluence found that, between 1937 and 1993, the area of
riparian forest and scrub decreased 28 percent, from 6,787 to 4,914 ac
(2,727 to 1,989 ha), and the herbaceous riparian vegetation decreased
from 4,076 to 780 ac (1,650 to 316 ha) (Jones and Stokes Associates,
Inc. 1998, Chap. 5, pp. 1-2). These losses are most likely attributed
to reduced stream flow down the river as a result of water diversions.
In the case of the San Joaquin River, efforts are under way for
restoring a more natural functioning hydrologic system and to restore
riparian habitat (San Joaquin River Restoration Program Record of
Decision 2012, pp. 7-8). Generally, in absence of ongoing dam
operations in such circumstances, the habitat is likely to regenerate
naturally; however, because of the way the majority of dams are
operated, these impacts are happening now and are likely to continue
for decades to come.
After the completion of the larger dams on the Colorado River
system starting in the 1930s, limited pulse flows reached the lower
Colorado River in Mexico for nearly 50 years, resulting in the loss of
cottonwood-willow forests and the establishment of tamarisk (Glenn et
al. 2001, pp. 1175-1186; Nagler et al. 2005, pp. 1843-1844). Local
decline of the yellow-billed cuckoo western DPS and other riparian
birds has been attributed to that habitat loss and degradation
(Hinojosa-Huerta et al. 2008, p. 81). Additionally, along the
R[iacute]o Altar in northern Mexico, completion of the
Cuauht[eacute]moc Dam and Reservoir (Presa Cuauht[eacute]moc) in 1950
diverted surface water and contributed to increased vegetation clearing
for agriculture, degradation of mature cottonwood forests, and
subsequent declines in distribution and abundance of riparian bird
species associated with these forests (Flesch 2008, p. 43), including
the yellow-billed cuckoo, which is known to occur there. In addition to
past habitat losses, the altered hydrology caused by dams continues to
have an ongoing impact on riparian habitat.
While alteration of hydrology due to dam construction and other
water supply projects has been widely implicated in the loss and
degradation of downstream riparian habitat for the western yellow-
billed cuckoo (Gaines and Laymon 1984, p. 73; Greco 1999, pp. 36-38;
Greco 2012, pp. 8-9), some dams have resulted in temporary habitat
expansion for the yellow-billed cuckoo within the immediate upstream
influence of the associated reservoirs. For example, one of the largest
concentrations of yellow-billed cuckoo in New Mexico occurs at the
inflow to Elephant Butte Reservoir on the middle R[iacute]o Grande
(Sechrist et al. 2009, p. 1; Ahlers et al. 2011, pp. 19-20). Yellow-
billed cuckoo numbers increased following several years when water
levels receded and riparian vegetation expanded into the exposed area
of the reservoir pool. The yellow-billed cuckoo population there
continues to increase, likely as a result of continued drawdown from
long-term drought that allows maturation of the riparian forest into
suitable breeding habitat (Ahlers et al. 2011, pp. 19-20). Drought
patterns are cyclical and, when wetter conditions return to the region,
Elephant Butte Reservoir likely will be refilled. When this happens,
approximately 92 percent of 44 to 87 pairs of yellow-billed cuckoos
there (detected during the 2007 and 2008 surveys) would be displaced
through inundation (Reclamation 2009, pp. 64-65).
The threat to the yellow-billed cuckoo's habitat from fluctuating
water levels behind dams is likely to occur elsewhere in the range of
the western yellow-billed cuckoo. In California, the State's second
largest population of yellow-billed cuckoos occurs within the inflow
delta footprint of Lake Isabella, a dammed reservoir on the Kern River.
Breeding yellow-billed cuckoos are also found at other reservoir inflow
deltas, such as Horseshoe Reservoir on the Verde River (Dockens and
Ashbeck 2011a, p. 1) and the Tonto Creek and Salt River inflows to
Roosevelt Lake in Arizona (Sferra 2012, in litt.).
The temporary gain in riparian habitat at the inflow of reservoirs
can be beneficial to the western yellow-billed cuckoo by providing
large expanses of additional nesting and foraging habitat during a
sequence of low-water years. However, the value of such habitat is
affected by fluctuating water levels between years. Drastically
fluctuating water levels with alternating inundation and desiccation
cycles have been associated with fluctuations in populations of western
yellow-billed cuckoos that breed in reservoir inflow sites (Laymon and
Williams 2002, pp. 12-13; Henneman 2008, pp. 12-13). For example, along
the Kern River, yellow-billed cuckoo numbers increased during low
reservoir levels for multiple years when vegetation recolonized the
drawdown area (Laymon et al. 1997, p. 10), but yellow-billed cuckoos
moved to other sites during a wet year when lake levels rose and
flooded out habitat (Launer et al. 1990, p. 10; Halterman et al. 2001,
p. 20). When the water receded, it took up to 2 years for yellow-billed
cuckoos to return to breed, but at reduced numbers (Laymon and Williams
2002, pp. 12-13; Henneman 2008, pp. 12-13), although the actual
mechanism needs further study (Henneman 2010, pp. 12-14). The water
level continues to remain below capacity at Lake Isabella due to dam
safety concerns (Stewart 2012, pers. comm.).
Once Lake Isabella fills again to capacity, the riparian habitat
that has since formed at the inflow and that supports cuckoos will
become
[[Page 61645]]
inundated, at least periodically (Whitfield 2012, pers. comm.), thereby
impacting the habitat of the western yellow-billed cuckoo. In addition,
the USACE and the USFS are developing a proposal and have completed a
final environmental impact statement (EIS) on options to repair dam
deficiencies and raise the height of the dam an additional 16 ft (4.9
m) (Isabella Lake Dam Safety Modification Project Environmental Impact
Statement Final October 2012). Pursuant to section 7 of the Act, a
biological opinion was completed for the proposed action, but the
yellow-billed cuckoo was not a species addressed in the section 7
consultation.
Lake Isabella is currently managed under long-term biological
opinions issued by the Service to the USACE and the USFS to address
impacts to the southwestern willow flycatcher (flycatcher) (Empidonax
traillii extimus) from reservoir operations and recreation (Service
1996, 1999, and 2005, entire). Some of the measures to conserve the
flycatcher in those biological opinions may be beneficial to the
western yellow-billed cuckoo; however, the eventual inundation of the
drawdown area of the reservoir will result in some degree of temporary
habitat loss and degradation under current conditions and may result in
permanent loss of habitat for the western yellow-billed cuckoo if the
proposed dam raise is implemented. Similar periods of inundation and
drawdown, resulting in corresponding development and destruction of
suitable yellow-billed cuckoo habitat, occurs at Roosevelt Lake (Salt
River Project (SRP) 2002, entire).
In Arizona, following the high water levels of 1983-1984 and 1986
on the Bill Williams River Delta, which is influenced by fluctuating
water levels from dams in the Colorado River system (Rosenberg et al.
1991, pp. 18-23), the yellow-billed cuckoo numbers declined by 70-75
percent. Habitat has since recovered on the Bill Williams River Delta,
but yellow-billed cuckoo numbers remained low for several years (Laymon
and Halterman 1987a, pp. 10-18). The actual mechanism that influences
the yellow-billed cuckoo's response to fluctuations in water levels is
unknown, but loss of prey has been implicated; areas that were
inundated normally support ground-nesting invertebrates, such as
katydids and sphinx moths, that yellow-billed cuckoos feed upon, and it
may take several years for these prey populations to rebound (Laymon
and Williams 2002, pp. 12-13; Henneman 2008, pp. 12-13).
In Sonora, Mexico, large dams exist on the Mayo, Yaqui, and Sonora
Rivers (Villase[ntilde]or 2006, p. 107). We do not have information on
the magnitude or frequency of effects, positive or negative, from water
management activities, to the western yellow-billed cuckoo in those
locations. However, we have no reason to believe that the dams are
managed in a substantially different manner in Mexico than in the
southwestern United States, and the effects to riparian habitat are
expected to be similar.
Despite some positive effects of dams on increasing western yellow-
billed cuckoo habitat in a few areas, these gains in habitat are only
temporary, and overall, the net effect of dams on the species has been
negative. As such, dams and their ongoing operations are a threat to
the western yellow-billed cuckoo over most of its range. This threat
has resulted in substantial historical losses of western yellow-billed
cuckoo habitat resulting in a curtailment of the DPS's range. The
ongoing operation of these dams is likely to have minor impacts to the
DPS at any given location, but because so many of the waterways within
the range of the DPS have been dammed, we believe this threat has a
substantial cumulative impact on the habitat of the western yellow-
billed cuckoo, especially when considered with other threats. Moreover,
we expect the operation of these dams will continue in a similar manner
for decades to come, and thus we expect this threat to be an ongoing
impact to the DPS's habitat.
The areas where the floodplain is still hydrologically connected to
the river and has relatively unconstrained riverflow, such as in some
areas of California and Sonora, Mexico, support the highest number of
western yellow-billed cuckoos (Villase[ntilde]or 2006, pp. 107-108;
Greco 2008, p. 6; Greco 2012, pp. 8-9). For example, the Sacramento
River from Red Buff to Colusa has a highly dynamic mosaic of habitat
patches of varying ages that form, disappear, and re-form in response
to active river channel processes that operate over decades (Greco
2008, p. 6; Greco 2012, pp. 8-9). Although this section of the
Sacramento River is also affected by altered hydrology, it is far
enough below Shasta Dam and below several major undammed tributaries,
such as Cottonwood Creek and Battle Creek, that it still has flood
events every few years that help support riparian habitat processes
(Werner 2012, pers. comm.). The river provides habitat characteristics
that Laymon (1998, p. 4) indicated were important for the yellow-billed
cuckoo in California, such as a meandering system with young riparian
habitat that, compared to mature woodlands, provides preferred nesting
sites, high productivity of invertebrate prey, and reduced predator
abundance (Laymon 1998, p. 4). Another example of relatively unimpacted
riparian habitat in the range of the western yellow-billed cuckoo is
found in the highlands of central Sonora, Mexico, which supports
occupied habitat of the yellow-billed cuckoo. Villase[ntilde]or (2005,
p. 108) found that the maintenance of the natural flooding regimes due
to the limited number of water development structures has allowed
riparian vegetation along sections of the Sonora, Moctezuma, and
Sahiaripa Rivers to persist in very good condition in some areas. Most
of the known occurrences of yellow-billed cuckoo in central Sonora are
associated with these regions.
Therefore, even though most of the dams within the range of the
western yellow-billed cuckoo were constructed in the past, dams
continue to affect both the downstream and upstream habitat through
alteration of flows. These effects can include widely fluctuating water
levels at inflow sites that inundate nesting habitat, limit food
resources, and flood or desiccate habitat (Poff et al. 1997, pp. 769-
784; Greco 1999, pp. 36-38; NAS 2002, pp. 145-150; Service 2002,
Appendix I, pp. 1-12). Downstream effects such as sediment retention
caused by controlled water flows, or sediment scouring and removal
caused by excessive water releases, do not mimic the natural flow
regimes and often result in the inability for cottonwoods to become
established or regenerate and provide habitat for the yellow-billed
cuckoo. Woody and herbaceous debris accumulates in the absence of these
scouring flows, increasing fire risk and intensity (Stromberg and Chew
2002, pp. 195-219) (see section on Wildfire below).
Dams and their flow modifications have ongoing effects to habitat
and will likely do so for decades to come, further modifying the
habitat of the western yellow-billed cuckoo. Furthermore, because a
relatively high proportion of individual yellow-billed cuckoos utilize
reservoir inflow areas, dam operations at those sites that result in
changes in water level can negatively affect a high proportion of the
western yellow-billed cuckoo. Therefore, direct and indirect
destruction of riparian habitat resulting from altered hydrology from
past dam-building activities continues to contribute to the curtailment
of the range of the western yellow-billed cuckoo. Additionally, as a
result of future predicted climate change (see Climate Change section
below), the climate within the range of the western yellow-billed
cuckoo will likely become
[[Page 61646]]
drier, which will increase the demand for water storage and conveyance
systems, which in turn will likely increase the frequency and severity
of impacts on western yellow-billed cuckoo habitat (Stromberg et al.
2013, pp. 411-415).
Surface and Ground Water Diversion
Water extractions, both from surface water diversions and ground
water pumping, can negatively affect riparian vegetation (Poff et al.
1997, pp. 769-784; Service 2002, Appendix I, pp. 1-8). Water diversions
and withdrawals can lower ground water levels in the vicinity of
riparian vegetation. Because ground water and surface water are
generally connected in floodplains, lowering ground water levels by
only about 3 ft (1 m) beneath riparian areas is sometimes sufficient to
induce water stress in riparian trees, especially in the western United
States (NAS 2002, p. 158). Physiological stress in native vegetation
from prolonged lower flows or ground water results in reduced plant
growth rate, morphological change, or mortality, as well as alters
species composition to favor more drought-tolerant vegetation, and
conversion to habitat dominated by nonnative species (Poff et al. 1997,
p. 776). These effects reduce and degrade habitat for the western
yellow-billed cuckoo for foraging, nesting, and cover.
Adverse effects of excessive ground water extraction on riparian
vegetation have been well documented in the southwestern United States.
Case histories on many river systems in Arizona including the Santa
Cruz River and on the Owens River in California have documented the
connection between overutilization of the ground water, lowering of the
water table, and the decline and eventual elimination of riparian
vegetation (Zektser et al. 2005, pp. 400-401; Webb and Leake 2006, pp.
317-320). Ground water extraction is also affecting river flows and
riparian vegetation along rivers that support the western yellow-billed
cuckoo in Mexico, including the R[iacute]o Conchos in Chihuahua (Kelly
and Aria-Rojo 2007, p. 174; Cornell et al. 2008, p. 98) and the
R[iacute]o Altar in Sonora, where the quantity of surface water
declined greatly between 2000 and 2007 (Flesch 2008, pp. 44-45).
Therefore, ground water extraction and water diversions create an
ongoing threat to western yellow-billed cuckoo habitat.
The hydrologic regime (stream flow pattern) and supply of (and
interaction between) surface and subsurface water is a driving factor
in the long-term maintenance, growth, recycling, and regeneration of
western yellow-billed cuckoo habitat (Service 2002, p. 16). As streams
reach the lowlands, their gradients typically flatten and surrounding
terrain opens into broader floodplains (Service 2002, p. 32). In these
geographic settings, the stream-flow patterns (frequency, magnitude,
duration, and timing) will provide the necessary stream-channel
conditions (wide configuration, high sediment deposition, periodic
inundation, recharged aquifers, lateral channel movement, and elevated
ground water tables throughout the floodplain) that result in the
development of western yellow-billed cuckoo habitat (Poff et al. 1997,
pp. 770-772; Service 2002, p. 16).
Allowing the river to flow over the width of the floodplain, when
overbank flooding occurs, is integral to allow deposition of fine moist
soils, water, nutrients, and seeds that provide the essential material
for plant germination and growth. An abundance and distribution of fine
sediments extending farther laterally across the floodplain and deeper
underneath the surface retains much more subsurface water, which in
turn supplies water for the development of the vegetation that provides
western yellow-billed cuckoo habitat and microhabitat conditions
(Service 2002, p. 16). The interconnected interaction between ground
water and surface water contributes to the quality of riparian
vegetation community (structure and plant species) and will influence
the ability of vegetation to regenerate and maintain itself as well as
germination, density, vigor, and composition (Arizona Department of
Water Resources 1994, pp. 31-32).
In many instances, western yellow-billed cuckoo breeding sites
occur along streams where human impacts are minimized enough to allow
more natural processes to create, recycle, and maintain the habitat.
However, there are also breeding sites that are supported by various
types of supplemental water including agricultural and urban runoff,
treated water outflow, irrigation or diversion ditches, reservoirs, and
dam outflows (Service 2002, p. D-15). Although the waters provided to
these habitats might be considered ``artificial,'' they are often
important for maintaining the habitat in appropriate condition for
breeding western yellow-billed cuckoos within the existing environment.
Encroachment of Levees and Flood Control and Bank Stabilization
Structures Into the River Channel and Floodplain
Other alterations in river hydrology with ongoing effects on
western yellow-billed cuckoo habitat include river channelization,
construction of levees, bank stabilization, and placement of any flood
control structures that encroach into the river and its floodplain.
These actions result in direct loss of habitat from construction and
from maintenance activities that remove woody vegetation that has
become established on the structures. Furthermore, these structures are
effective, by design, at severing the hydrologic connection of the
river's main channel and the river's immediate floodplain, thereby
preventing overbank flooding. By preventing overbank flooding, levees
and other similar structures reduce the amount of water available to
riparian vegetation in the floodplain, which results in desiccation and
eventual loss and degradation of riparian habitat (Vogl 1980, pp. 84-
86; NAS 2002, p. 155; Greco 2012, pp. 8-9). Such effects are less
destructive, however, for those levees located farther from the stream
system, such as those outside the meander belt of a river (Greco 2012,
p. 4).
As an illustrative example, we provide a brief summary of how river
channelization, construction of levees close to the river, and rock
riprap armoring along the levees have caused destruction and
modification of yellow-billed cuckoo habitat on the Sacramento River,
one of the most substantial historical nesting and foraging habitat
areas for the DPS. The Sacramento River is now disconnected from
ecological processes that both renew and restore riparian and aquatic
habitats (Laymon and Halterman 1987a, pp. 11-14; Halterman 1991, pp. 1-
2; Greco 2008, p. 6; Greco 2012, pp. 8-9). More than one-half of the
Sacramento River's banks within the lowermost 194 mi (312 km) of river
have now been rip-rapped by 40 years of bank protection (Service 2000,
pp. 26-29). Rock riprap armoring a river reach often changes the river
dynamics and leads to cutting and erosion immediately downstream from
the riprap. Therefore, riprapping banks leads to the need for more
riprapping, a repeating process that is not complete until the entire
river is channelized.
Channelizing the river and severing the connection to the
floodplain has severely altered the natural disturbance regime that
would have allowed riparian habitat to regenerate now and in the future
(Poff et al. 1997, pp. 769-784; Greco 2008, p. 6; Greco 2012, pp. 8-9).
The result is that much of the river's remaining riparian habitat is
modified, and now occurs in narrow, disconnected, linear strips
(Service 2000, pp. 26-29; Halterman et al. 2001, p. 4) that are not
utilized by the yellow-
[[Page 61647]]
billed cuckoo for breeding (Gaines 1974, p. 204; Greco 2012, p. 9).
With the example of the Sacramento River, nesting yellow-billed cuckoos
no longer occur south of Colusa as the river has been channelized and
riprapped from that point to the Sacramento San Joaquin River Delta.
These flood control and bank stabilization structures also keep the
riparian habitat from regenerating and maturing. The factors that
reduce yellow-billed cuckoo breeding in these areas are not well
understood, but reductions of breeding population have been attributed
to lack of patches of adequate size for nesting (Greco 2012, pp. 8-9),
increased predators, and the species inability to use highly isolated
patches (Halterman 1991, pp. 33-38), as discussed under Factor E. The
Sacramento River is but one of many rivers within the range of the
western yellow-billed cuckoo where these activities have destroyed and
modified riparian habitat and where the ramifications of these past
actions are continuing to impact the DPS's habitat today. These ongoing
impacts will likely continue for decades to come.
Transportation Systems
Similarly, transportation systems have directly and indirectly
altered a large number of riparian areas in western North America (NAS
2002, p. 182). Road and rail systems are frequently sited along rivers,
and often entail removing riparian vegetation for construction of the
roadbed, and modifying local hydrology to reroute surface water and
ground-water. Bridges or culverts require abutments along the bank to
provide roadway support. Because abutments and roadbeds physically
constrain the stream, future lateral adjustments by the stream, which
can affect floodplain dynamics, are effectively eliminated, which
reduces and degrades riparian habitat (NAS 2002, p. 182). Such impacts
result in additional destruction and modification of habitat for the
western yellow-billed cuckoo. In comparison with construction of dams
and altered hydrology this threat, by itself, is less likely to result
in severe impacts to riparian habitat; however, this threat is but one
of many that, in combination, result in substantial changes to physical
and hydrological properties of a watercourse, which in turn contributes
to a substantial curtailment in the habitat of the western yellow-
billed cuckoo.
Gravel Mining
Other past and ongoing effects to riparian habitat result from
gravel mining (Kondolf et al. 2001, pp. 54, 59). Extraction of gravel,
primarily for construction products, typically occurs along rivers and
adjacent floodplains where gravel deposits are naturally found. Large
amounts of gravel removal from the stream and active floodplain result
in channel downcutting or incision, which affects groundwater levels,
frequency of overbank flows, bank stability, and the extent and
character of riparian vegetation of specific stream reaches (Collins
and Dunne, 1989, pp. 213-224; Kondolf 1995 pp.133-136; NAS 2002, p.
179). Some examples of downcutting on streams in California that
historically had, but no longer have, populations of yellow-billed
cuckoos, include: Cache Creek, Yolo County (15.0 ft (4.6 m) average and
26.0 ft (8.2 m) maximum downcutting); Merced River, Merced County (5.9
ft (1.8 m) average and 7.8 ft (2.4 m) maximum downcutting); Putah
Creek, Yolo County (7.8 ft (2.4 m) average and 15.0 ft (4.6 m) maximum
downcutting); Russian River, Sonoma County (11.4 ft (3.5 m) average and
17.9 ft (5.5 m) maximum downcutting); and Santa Clara River, Ventura
County (15.6 ft (4.8 m) average and 20.2 ft (6.2 m) maximum
downcutting) (Kondolf et al. 2001, p.50).
Furthermore, gravel extraction creates a knickpoint (a sharp change
in channel slope) that typically erodes upstream in a process known as
headcutting, which has the potential to propagate upstream for miles on
the main river and its tributaries. As headcuts migrate upstream, the
incision propagates upstream (Kondolf et al. 2001, p. 49). This process
creates ongoing and future impacts to habitat from past as well as
current gravel mining operations. Similar to the effects of manmade
levees when they disconnect floodplain habitat from the active river
channel, artificial channel incision as a result of gravel mining and
similar activities reduces overbank flooding. This situation reduces
the hydrological connection to the floodplain (Kondolf et al. 2001, p.
56), thereby resulting in subsequent loss and degradation of riparian
habitat for the western yellow-billed cuckoo, throughout its range,
including Mexico (Cornell et al. 2008, p. 98). The effects of incision
and channel erosion are further exacerbated where gravel mining occurs
in sediment-starved reaches below dams (Kondolf et al. 2001, p. 10). We
expect past and ongoing gravel mining activities, either alone or in
combination with other hydrological changes in riparian areas, to
continue to modify habitat and further curtail the range of the western
yellow-billed cuckoo for decades.
In conclusion, dams, channelization, and other manmade features
that alter the watercourse hydrology and encroach into the active
channel and floodplain are threats to the habitat of the western
yellow-billed cuckoo because they, separately or in combination,
significantly reduce and degrade nesting and foraging habitats. The
natural processes that sustain riparian habitat in these and similar
dammed and channelized river systems in the American West and in
northwestern Mexico have been altered, resulting in only fragments or
remnants of formerly large tracts of native riparian forests that no
longer support breeding yellow-billed cuckoos. The multiple effects
from altered hydrology comprise the most widespread and greatest
magnitude of current threats to habitat that supports the western
yellow-billed cuckoo. Such effects continue to modify habitat and
further curtail the range of the western yellow-billed cuckoo.
Moreover, we expect these alterations in the hydrology to continue to
affect habitat of the western yellow-billed cuckoo into the future.
Habitat Loss and Degradation From Agricultural Activities
Following the effects from alterations in hydrology, in severity,
conversion of riparian areas for agricultural crops and livestock
grazing has been, and continues to be, a major contributor to riparian
habitat loss and degradation (NAS 2002, p. 161; Johnson et al. 2007, p.
61).
Large areas of cottonwood-willow floodplain vegetation have been
converted to agricultural uses, further reducing the extent of habitat
available to western yellow-billed cuckoos for breeding (Swift 1984,
pp. 225-226; Rosenberg et al. 1991, pp. 18-23). For example, within
areas that support the yellow-billed cuckoo, clearing for agricultural
uses occurred extensively in the past. On the floodplains of the
Sacramento River (Greco 1999, pp. 2, 107), riparian habitat was reduced
from 775,000 ac (314,000 ha) in the 1850s to less than 18,000 ac (7,287
ha) by 1977 (Swift 1984, p. 226). Clearing for agriculture is also
extensive along the lower Colorado River (Rosenberg et al. 1991, pp.
18-23), San Pedro River, Gila River (Swift 1984, p. 226), R[iacute]o
Grande, and several river courses in northern Mexico including, but not
limited to, the R[iacute]o Yaqui, R[iacute]o Mayo, R[iacute]o Bambuto,
R[iacute]o Tubutama, and R[iacute]o Sonora (Russell and Monson 1998, p.
11; IMADES 2003, p. 4; Villase[ntilde]or 2006, p. 108). Clearing also
occurred along the coasts of Sinaloa and southern Sonora, Mexico,
resulting in massive losses of thorn forest to
[[Page 61648]]
industrial agriculture (Rohwer et al. 2009, p. 19054).
Although most riparian and thorn scrub habitat losses largely stem
from past agricultural clearing, effects from cultivated agricultural
lands are ongoing. Agricultural lands continue to dominate much of the
remaining riparian landscape, particularly along the Sacramento (Greco
1999, pp. 94, 104, 107), parts of the Gila, and lower Colorado Rivers
(Johnson et al. 2007, p. 207); along the latter, 65 percent of yellow-
billed cuckoo survey sites are bordered on at least one side by
agriculture fields (Johnson et al. 2007. p. 61). Riparian areas are
sometimes viewed as a potential source of plant and animal pests, a
source of shade that may reduce crop yields, and competition for scarce
water resources (NAS 2002, pp. 170-171). For example, in the Salinas
Valley in California, a vigorous program is under way to comply with
food safety practices that involve the clearing of riparian habitat
adjacent to certain types of crops in an effort to eliminate wildlife
presence, which has been linked to contamination of crops with a
virulent strain of the bacteria Escherichia coli (Beretti and Stuart
2008, pp. 68-69). While yellow-billed cuckoos do not currently breed
along the Salinas River (Gaines and Laymon 1984, p. 52), if these same
rules are applied to farmland along the Gila, Rio Grande, Sacramento
and Colorado Rivers, yellow-billed cuckoo habitat will be eliminated to
meet these food safety concerns.
Accidental fire from farm workers operating machinery or burning
weeds sporadically escapes into adjacent riparian habitat. Recent fires
on western yellow-billed cuckoo and southwestern willow flycatcher
conservation properties occurred in 2011, burning 58 ac (24 ha) and 6
ac (2 ha), respectively, within the Fort Thomas Preserve, on parcels
owned by the Salt River Project and U.S. Bureau of Reclamation. Both
fires were determined to be human-caused, likely from farm workers
burning weeds along irrigation drains (SRP 2011, p. 39).
Other ongoing effects from cultivated agriculture on the western
yellow-billed cuckoo are addressed under Factor E. These include
fragmentation of habitat into smaller, more widely disjunct patches,
ongoing influence of agriculture on riparian bird community
composition, and effects from pesticides, which can negatively impact
insect prey populations of the western yellow-billed cuckoo.
Domestic livestock grazing is a traditional agricultural land use
practice in the southwestern United States since at least the 1600s
(Little 1992, p. 88; Clary and Kruse 2004, p. 239). Livestock grazing
continues to be a widespread agricultural use of riparian areas in the
western United States and is one of the most common sources of past and
ongoing riparian habitat degradation (Carothers 1977, p. 3; Rickard and
Cushing 1982, pp. 2-4; Cannon and Knopf 1984, p. 236; Klebenow and
Oakleaf 1984, p. 202; Swift 1984, pp. 225-226; Clary and Webster 1989,
pp. 1-2; Schultz and Leininger 1990, pp. 298-299; Bock et al. 1993, p.
300). Livestock grazing occurs in yellow-billed cuckoo habitat along
sections of the middle Rio Grande in New Mexico (Lehmann and Walker
2001, p. 12), R[iacute]o Conchos (Cornell et al. 2008, p. 96),
R[iacute]o Bambuto, Tubutama, La Reforma, Cuchujaqui River in Alamos,
Aconchi and Baviacora in R[iacute]o Sonora, and upper San Pedro River
(IMADES 2003, p. 4), and several other rivers in central Sonora, Mexico
(Villase[ntilde]or 2006, p. 108). Grazing also occurs extensively along
watercourses in a protected reserve on the R[iacute]o Aros and
R[iacute]o Yaqui in Sonora, Mexico, where the yellow-billed cuckoo has
been documented (O'Brien et al. 2008, p. 8). Grazing intensity in
northern Sonora, Mexico, is generally much higher than in adjacent
Arizona (Balling 1988, pp. 106-107; Flesch 2008, pp. 44-45), which
leads to greater degradation of riparian habitat than in Arizona.
The Service (2002, Appendix G, pp. 5-7) and Krueper et al. (2003,
p. 608) reviewed the effects of livestock grazing, primarily in
southwestern riparian systems. The frequency and intensity of effects
vary across the range of the species, due to variations in grazing
practices, climate, hydrology, ecological setting, habitat quality, and
other factors (Service 2002, Appendix G, p. 1). However, these effects
generally include the removal and trampling of vegetation and
compaction of underlying soils, which can inhibit germination and
change hydrology (Rea 1983, p. 40; Belsky et al. 1999, pp. 419-431) and
promote the dispersal of nonnative plant species. Such effects are most
significant when riparian areas have been subject to overuse by
livestock (NAS 2002, pp. 24, 168-173). Overuse occurs when grazed
vegetation does not recover sufficiently to maintain itself and soils
are left bare and vulnerable to erosion. Over time, livestock grazing
in riparian habitats, combined with other alterations in streamflow,
typically results in reduction of plant species diversity and density,
and may increase the distribution and density of nonnative tamarisk by
eliminating competition from native cottonwood and willow saplings,
which are preferred forage for livestock (Krueper et al. 2003, p. 608).
Long-term cumulative effects of livestock grazing involve changes
in the structure and composition of riparian vegetation (Service 2002,
Appendix G, pp. 5-7), which may affect suitability of habitat for
yellow-billed cuckoo breeding and prey population abundance. The
western yellow-billed cuckoo nesting habitat is structurally complex
with tall trees, a multistoried vegetative understory, low woody
vegetation (Halterman 1991, p. 35) and higher shrub area than sites
without yellow-billed cuckoos (Hammond 2011, p. 48). Livestock grazing
alters understory vegetation, reducing height and density or
eliminating new growth in riparian areas, and thereby hampering
recruitment of woody species that, when mature, provide nest sites.
Furthermore, the relatively cool, damp, and shady areas favored by
yellow-billed cuckoos are those favored by livestock over the
surrounding drier uplands. This can concentrate the effects of habitat
degradation from livestock in western yellow-billed cuckoo habitat
(Ames 1977, p. 49; Valentine et al. 1988, p. 111; Johnson 1989, pp. 38-
39; Clary and Kruse 2004, pp. 242-243).
Removal, reduction, or modification of cattle grazing has resulted
in increases in abundance of some riparian bird species. For example,
Krueper (1993, pp. 322-323) documented responses of 61 bird species,
most of which increased significantly 4 years after removal of
livestock grazing in Arizona's San Pedro River Riparian National
Conservation Area (NCA). The bird species guilds that increased most
dramatically were riparian species, open-cup nesters, Neotropical
migrants, and insectivores, all species that share characteristics with
the yellow-billed cuckoo. The yellow-billed cuckoo numbers in the study
increased, although not significantly (p=0.13) (Krueper 2003, p. 612)
but their survey methodology was not designed to detect yellow-billed
cuckoos. Recovery of vegetation in response to grazing removal in that
study was quickest and most pronounced in the lower vegetation layers,
the most accessible to grazing cattle. Thus, this situation would allow
a greater number of seedlings and saplings of cottonwoods and other
nest trees to attain maturity as suitable nesting sites.
In another example, livestock grazing was terminated along portions
of the South Fork Kern River at the Kern River Preserve in the 1980s,
and yellow-billed
[[Page 61649]]
cuckoos increased in number in the years following livestock removal.
Smith (1996, p. 4) contended that termination of grazing at the Kern
River Preserve was responsible for the dramatic increase in riparian
vegetation, which was concurrent with the increase in yellow-billed
cuckoo numbers. These examples suggest that even severely degraded
riparian systems can recover quickly, in at least some cases, after
livestock removal (Krueper 2003, p. 615), and that damage to riparian
vegetation from grazing is at least partly reversible. They also
illustrate the extent to which livestock grazing destroys and modifies
nesting and foraging habitat of the western yellow-billed cuckoo.
In conclusion, most of the direct loss of habitat from farming has
occurred in the past, but ongoing agricultural activities, in whole or
in combination with other impacts, especially those that result in
changes in a watercourse's hydrology, have resulted in the curtailment
of nesting and foraging habitat for the western yellow-billed cuckoo by
restricting or preventing the growth of riparian plants, and such
activities present an ongoing threat. Most of the current impacts from
agricultural land uses arise from livestock overgrazing in riparian
areas. Riparian vegetation can recover relatively quickly from these
effects after livestock removal (Smith 1996, p. 4; Krueper 2003, p.
615). However, without proper management to reduce overgrazing, ongoing
overgrazing will continue to contribute to habitat modification in the
range of the western yellow-billed cuckoo into the future.
Habitat Loss and Degradation Due to Conversion to Nonnative Vegetation
Throughout most of its range, habitat for the western yellow-billed
cuckoo is threatened by the conversion of native riparian woodlands to
riparian vegetation dominated by tamarisk and other nonnative
vegetation. The major threat from this habitat conversion is the change
from vegetation that supplies the western yellow-billed cuckoos with
essential food and adequate thermal cover to vegetation that does not
supply these attributes. The establishment and persistence of tamarisk
is often, but not always, aided by altered hydrology, as described
above. Altered hydrology is not the cause for establishment and
persistence of other types of nonnative vegetation; therefore, we
present information on nonnative vegetation in this separate section.
Tamarisk is the most widespread nonnative woody plant species found
in habitat for the western yellow-billed cuckoo. Glenn and Nagler
(2005, pp. 420-423) provide most of the following overview of tamarisk.
Tamarisk is present in nearly every southwestern riparian plant
community, but varies in dominance from stream to stream. On streams
where altered hydrology can no longer support native species, it has
replaced native plant communities entirely, but occurs at a low
frequency on other streams. Tamarisk was introduced into western North
America in the 1800s to serve as ornamental windbreaks, and for erosion
control and other purposes. Several species escaped cultivation and
have since spread rapidly. The center of distribution is currently
Arizona, New Mexico, and Utah, and tamarisk has spread throughout most
of the range of the western yellow-billed cuckoo at least as far north
as the Yellowstone River in Montana in the Rockies, and at least as far
south as the Yaqui River Valley in Sonora, Mexico. Recent studies in
the northwest have located major populations of tamarisk in
southwestern Idaho, and eastern Washington and Oregon. Models based on
projected climate change predict that this invasive species will become
more dominant in this region over the next 100 years (Kerns et al
2009). Tamarisk also occurs west to the Owens, San Joaquin, and
Sacramento Rivers in California, although it is still nearly absent
from the mainstem Sacramento River in California, and suitable habitat
west of the Cascades in Oregon and Washington.
Tamarisk also occurs as isolated individuals along sections of the
Sonora, Moctezuma, and Sahiaripa Rivers in Sonora, Mexico, where the
hydrology has been little altered by human modifications
(Villase[ntilde]or 2006, pp. 107-108). Its presence is highly variable
within sections of the R[iacute]o Conchos in Chihuahua, Mexico, and
becomes dominant in some reaches of that river (Kelly and Arias Rojo
2007, pp. 177-178; Cornell et al. 2008, p. 4).
The threshold (in terms of percent tamarisk) for abandonment of a
riparian system by western yellow-billed cuckoos is not known. They are
not found in areas that are totally dominated by tamarisk with the
complete lack of willows or cottonwoods. In California, two native-
dominated areas occupied in 1977 by several pairs of yellow-billed
cuckoos had, by 1986, converted to monotypic stands of tamarisk and
were found to be uninhabited by yellow-billed cuckoos. For example,
above Laguna Dam on the Colorado River in 1977 at least three pairs of
yellow-billed cuckoos occupied a 30-ac (12-ha) site that was
approximately 20-40 percent willow (Laymon and Halterman 1987a, p. 12).
By 1986 no yellow-billed cuckoos were detected on the site where the
dominant vegetation had become tamarisk, with less than 1 percent
willow cover. In the vicinity of Picacho State Recreation Area, on the
California side of the Colorado River, in 1977, 21 yellow-billed
cuckoos were found in 297 ac (120 ha) of a 230-ft-wide (70-m-wide)
willow forest (Gaines and Laymon 1984, p. 72). By 1986, tamarisk and
aquatic vegetation dominated this area, and no yellow-billed cuckoos
were found in the 12 ac (5 ha) of scattered willow-cottonwood habitat
that remained (Laymon and Halterman 1987a, pp. 12-13).
Human disturbance, such as water diversion, flood control,
vegetation clearing, and improper grazing management, often facilitates
replacement of native vegetation with tamarisk (Kerpez and Smith 1987,
pp. 1-5; Hunter et al. 1988, p. 113; Rosenberg et al. 1991, pp. 18-23).
Altered hydrologic regimes (flooding or reduction in water flows from
dams) has disrupted natural flooding events that are essential for
maintaining native riparian ecosystems (Vogl 1980, pp. 84-86; Rosenberg
et al. 1991, pp. 18-23), and the disruption (usually elimination) of
flooding tends to favor tamarisk. In contrast to native cottonwoods,
tamarisk does not need flooding to regenerate (Kerpez and Smith 1987,
pp. 1-5).
Tamarisk is also tolerant of high salt levels, which can be present
in river systems as a combined result of water diversions that lower
the near-surface ground water and irrigation water runoff that contains
high levels of dissolved salts (Kerpez and Smith 1987, pp. 1-5; Busch
and Smith 1993, pp. 186-194). This higher tolerance to water stress and
salt accumulation is a principle mechanism by which tamarisk has become
dominant on some regulated western rivers (Glenn and Nagler 2005, p.
439). In addition, tamarisk takes salts from the ground water and
exudes them from its leaves, rendering the soil even more unsuitable
for germination of native riparian vegetation. This is a significant
problem in streams with artificially reduced streamflows where salts
accumulate and are not flushed from the system. These factors favor
regeneration of tamarisk over native trees and shrubs and are an
ongoing threat. Additional areas of native habitat are continuing to be
lost to this process. In summary, the persistence and expansion of
tamarisk-dominated habitat is the result of multiple forms of ongoing
human-related disturbances, which result in degradation of native-
[[Page 61650]]
dominated riparian habitat, thus reducing its suitability as breeding
habitat for the western yellow-billed cuckoo.
Other nonnative tree and shrub species have become established
within the range of the western yellow-billed cuckoo. In western
Colorado and Utah, Russian olive (Elaeagnus angustifolia) has become
established and is a dominant tree species in many riparian systems.
Giant reed (Arundo donax), common edible fig (Ficus carica), and the
Himalayan blackberry (Rubus discolor) are some of the more conspicuous
nonnative plants widely established along the Sacramento River, with
Himalayan blackberry dominating the understory at some restoration
sites (Borders et al. 2006, p. 310). Along the Sacramento River,
yellow-billed cuckoos were far less likely to be detected at sites with
an understory dominated by Himalayan blackberry than sites with a
predominant native understory. Himalayan blackberry may prevent
establishment of native understory species due to its dense growth
habit (Hammond 2011, pp. 48-49). Nesting of the yellow-billed cuckoo
has not been documented in riparian stands dominated by giant reed,
common fig, or Himalayan blackberry that lack at least some native
canopy trees.
In conclusion, because of the absence or near absence of nesting by
yellow-billed cuckoos in nearly monotypic stands of tamarisk and other
nonnative vegetation, the available literature suggests that conversion
of native or mixed (native and nonnative) riparian woodlands to nearly
monotypic stands of tamarisk and other nonnative vegetation, coupled
with the inability of native vegetation to regenerate under altered
hydrological conditions, is a significant threat to the western yellow-
billed cuckoo now and in the future. Nonnative vegetation occurs across
most of the range of the western yellow-billed cuckoo; its
establishment can be caused by altered hydrology or other disturbances,
which are widespread throughout the range. We expect nonnative
vegetation to increasingly modify and curtail habitat for the western
yellow-billed cuckoo within a majority of its range in the United
States and northern Mexico into the future.
Use of Tamarisk by Western Yellow-billed Cuckoos and the Spread of the
Introduced Tamarisk Leaf Beetle Into the Southwest
Yellow-billed cuckoos use habitat with a tamarisk component for
nesting in southern California, Arizona, and western New Mexico, but
are not found in monotypic stands of tamarisk. Yellow-billed cuckoo
presence in tamarisk-dominated habitats does not necessarily equate to
habitat suitability (Sogge et al. 2008, p. 149; Hammond 2011, p. 50),
and additional research is needed to determine productivity,
survivorship, physiological condition, and food availability in these
habitats. Healthy native riparian vegetation provides much better
habitat for the species.
Tamarisk can add to foliar cover that contributes toward reducing
temperatures in riparian areas (Paxton et al. 2011, p. 259). Even
relatively small decreases in foliar cover may render a site unsuitable
for nesting western yellow-billed cuckoos (Paxton et al. 2011, p. 260).
Removal of tamarisk in drainages occupied by western yellow-billed
cuckoos could be considered a threat if the removal leaves little or no
woody vegetation and native riparian vegetation is unable to
reestablish. The available literature that pertains to riparian
restoration in New Mexico and Arizona (Poff et al. 1997, pp. 769-784;
Glen and Nagler 2005, pp. 439-441; Sogge et al. 2008, pp. 151-152;
Stromberg et al. 2009, pp. 181-182) suggests that restoration of
natural hydrological processes, rather than direct removal programs,
would be a more effective method for promoting regeneration of native
riparian vegetation and diminishing the presence of tamarisk. However,
tamarisk removal programs coupled with native riparian plantings can
speed up the restoration process assuming that the hydrologic system
will support the native vegetation.
Tamarisk leaf beetle insects (leaf beetles) (Diorhabda spp.) were
released into many locations throughout the southwest to control
tamarisk. Leaf beetles are now spreading within the more arid range of
the yellow-billed cuckoo in Nevada, Utah, Arizona, New Mexico, and
Texas. Defoliation of tamarisk by the beetles occurs in the summer
months when western yellow-billed cuckoos are in the process of
nesting. Tamarisk leaf beetles could eventually occur throughout the
western United States and northern Mexico (Tracy et al. 2008, pp. 1-3).
The future effects of the beetle introductions to the western yellow-
billed cuckoo are unknown. If beetles succeed in killing tamarisk,
western yellow-billed cuckoo numbers may decline in areas where the
hydrology is no longer capable of supporting a native riparian habitat
and the numbers may increase in areas where native riparian vegetation
is able to become reestablished.
Wildfire
Historically, wildfire was uncommon in native riparian woodlands
(Busch and Smith 1993, pp. 186-194). However, the lack of scouring
floods on regulated and unregulated rivers has resulted in the
accumulation of fuel on the floodplain, which increases fire risk and
intensity (Stromberg and Chew 2002, pp. 195-219). Water withdrawal,
dams, climate change, drought, and human use also contribute toward an
increased fuel load and probability of wildfire occurrence. Most fires
today are human-caused (Service 2002, p. L-8). In degraded habitat with
tamarisk the threat of fire may be greater. Tamarisk ignites quickly,
further increasing the incidence of periodic fires. Exacerbating the
immediate loss of native trees from fire, tamarisk recovers more
quickly than native trees (Glenn and Nagler 2005, pp. 435-436). Along
the Rio Grande River in New Mexico and Texas, wildfire has been
documented as destroying, degrading, or setting back successional
stages of vegetation development of yellow-billed cuckoo habitat
(Sproul 2000, p. 3). In summary, the alteration of riparian systems
through changes in hydrologic functioning and the introduction of
nonnative tamarisk have increased the incidence of wildfire into
yellow-billed cuckoo habitat. These fires further degrade, isolate, or
fragment yellow-billed cuckoo habitat.
Environmental Impacts of Cross Border Foot Traffic in the Southwest
The environmental impact caused by cross border foot traffic has
been increasingly occurring in more fragile and remote areas. The
number of U.S. Border Patrol apprehensions of border crossers varies
annually. Between October 1, 1999, and September 30, 2012, a yearly
average of 333,517 border crossers were apprehended by the United
States Border Patrol in the Tucson Sector, which does not account for
the many others who were not caught (U.S. Border Patrol 2013, p. 1).
Impacts associated with border crossings include creation of erosion
and watershed degradation, loss of vegetation and wildlife, and human-
caused wildfire (Defenders of Wildlife 2006, pp. 1-42). Drainages used
by border crossers include the San Pedro River, Santa Cruz River,
Cienega Creek, and many remote drainages in the mountain ranges of
southeastern Arizona.
Human-caused wildland fires have been particularly damaging to
areas of riparian habitat in Arizona, especially within 100 mi (161 km)
of the United
[[Page 61651]]
States-Mexico border where border crossers are known to set fires to
divert law enforcement agents. Border crossers are also responsible for
campfires that can escape and spread as wildfires. At least 2,467
wildfires began along the Arizona border with Mexico from 2006 to 2010
(Government Accounting Office (GAO) 2011, p. 1). Federal officials have
officially investigated only 77 of those fires. Of the fires
investigated, 30 were started by border crossers. The resulting
environmental impacts include the expansion of nonnative plant species,
degraded endangered species habitat, and soil erosion.
Climate Change
Climate change may be impacting the western yellow-billed cuckoo.
Climate change is discussed here under Factor A because, although it
may affect the western yellow-billed cuckoo directly by creating
physiological stress, the primary impacts of climate change on the
species are expected to be through changes in the availability and
distribution of western yellow-billed cuckoo habitat.
Our analyses under the Act include consideration of ongoing and
projected changes in climate. The terms ``climate'' and ``climate
change'' are defined by the Intergovernmental Panel on Climate Change
(IPCC). The term ``climate'' refers to the mean and variability of
different types of weather conditions over time, with 30 years being a
typical period for such measurements (IPCC 2007a, p. 78). The term
``climate change'' thus refers to a change in the mean or variability
of one or more measures of climate (for example, temperature or
precipitation) that persists for an extended period, whether the change
is due to natural variability or human activity (IPCC 2007a, p. 78).
Scientific measurements spanning several decades demonstrate that
changes in climate are occurring, and that the rate of change has
increased since the 1950s. Examples include warming of the global
climate system, and substantial increases in precipitation in some
regions of the world and decreases in other regions (for these and
other examples, see IPCC 2007a, p. 30; Solomon et al. 2007, pp. 35-54,
82-85). Results of scientific analyses presented by the IPCC show that
most of the observed increase in global average temperature since the
mid-20th century cannot be explained by natural variability in climate
and is ``very likely'' (defined by the IPCC as 90 percent or higher
probability) due to the observed increase in greenhouse gas (GHG)
concentrations in the atmosphere as a result of human activities,
particularly carbon dioxide emissions from use of fossil fuels (IPCC
2007a, pp. 5-6 and figures SPM.3 and SPM.4; Solomon et al. 2007, pp.
21-35). Further confirmation of the role of GHGs comes from analyses by
Huber and Knutti (2011, p. 4), who concluded it is extremely likely
that approximately 75 percent of global warming since 1950 has been
caused by human activities.
Scientists use a variety of climate models, which include
consideration of natural processes and variability, as well as various
scenarios of potential levels and timing of GHG emissions, to evaluate
the causes of changes already observed and to project future changes in
temperature and other climate conditions (for example, Meehl et al.
2007, entire; Ganguly et al. 2009, pp. 11555, 15558; Prinn et al. 2011,
pp. 527, 529). All combinations of models and emissions scenarios yield
very similar projections of increases in the most common measure of
climate change, average global surface temperature (commonly known as
global warming), until about 2030. Although projections of the
magnitude and rate of warming differ after about 2030, the overall
trajectory of all the projections is one of increasing global warming
through the end of this century, even for the projections based on
scenarios that assume that GHG emissions will stabilize or decline.
Thus, there is strong scientific support for projections that warming
will continue through the 21st century, and that the magnitude and rate
of change will be influenced substantially by the extent of GHG
emissions (IPCC 2007a, pp. 44-45; Meehl et al. 2007, pp. 760-764, 797-
811; Ganguly et al. 2009, pp. 15555-15558; Prinn et al. 2011, pp. 527,
529). See IPCC 2007b, p. 8, for a summary of other global projections
of climate-related changes, such as frequency of heat waves and changes
in precipitation. Also see IPCC 2011 (entire) for a summary of
observations and projections of extreme climate events.
Various changes in climate may have direct or indirect effects on
species. These effects may be positive, neutral, or negative, and they
may change over time, depending on the species and other relevant
considerations, such as threats in combination and interactions of
climate with other variables (for example, habitat fragmentation) (IPCC
2007a, pp. 8-14, 18-19). Identifying likely effects often involves
aspects of climate change vulnerability analysis. Vulnerability refers
to the degree to which a species (or system) is susceptible to, and
unable to cope with, adverse effects of climate change, including
climate variability and extremes. Vulnerability is a function of the
type, magnitude, and rate of climate change and variation to which a
species is exposed, its sensitivity, and its adaptive capacity (IPCC
2007a, p. 89; see also Glick et al. 2011, pp. 19-22). There is no
single method for conducting such analyses that applies to all
situations (Glick et al. 2011, p. 3). We use our expert judgment and
appropriate analytical approaches to weigh relevant information,
including uncertainty, in our consideration of the best scientific
information available regarding various aspects of climate change.
Global climate projections are informative, and, in some cases, the
only or the best scientific information available for us to use.
However, projected changes in climate and related impacts can vary
substantially across and within different regions of the world (IPCC
2007a, pp. 8-12). Therefore, we use ``downscaled'' projections when
they are available and have been developed through appropriate
scientific procedures, because such projections provide higher
resolution information that is more relevant to spatial scales used for
analyses of a given species (see Glick et al. 2011, pp. 58-61, for a
discussion of downscaling). With regard to our analysis for the western
yellow-billed cuckoo, downscaled projections are available.
The Southwest is already experiencing the impacts of climate
change. The region has heated up markedly in recent decades, and the
period since 1950 has been hotter than any comparably long period in at
least 600 years (Graumlich 1993, pp. 249-255; Salzer and Kipfmueller
2005, pp. 465-487; Millar et al. 2006, pp. 273-287; Ababneh 2008, pp.
59-78; Bonfils et al. 2008, pp. 6404-6424; Stevens et al. 2008, pp. 1-
15; Salzer et al. 2009, pp. 20348-20353; Woodhouse et al. 2010, pp.
21283-21288; Hoerling et al. 2012, pp. 74-92). The decade 2001-2010 was
the warmest in the 110-year instrumental record, with temperatures
almost 2[deg]F higher than historic averages, with fewer cold snaps and
more heat waves (Hoerling et al. 2012, pp. 74-92). Compared to
temperature, precipitation trends vary considerably across the region,
with portions experiencing both decreases and increases (Hoerling et
al. 2012, pp. 74-92). There is mounting evidence that the combination
of human-caused temperature increases and recent drought has influenced
widespread tree mortality (Van Mantgem et al. 2009, pp. 521-524; Allen
et al. 2010, pp. 660-684), increased fire
[[Page 61652]]
occurrence and area burned (Westerling et al. 2006, pp. 940-943), and
forest insect outbreaks (Bentz et al. 2010, pp. 602-613). Human-caused
temperature increases and drought have also caused earlier spring
snowmelt and shifted runoff to earlier in the year (Barnett et al.
2008, pp. 1080-1083).
There are three predictions for anticipated effects from climate
change in the southwestern United States and parts of northwestern
Mexico. First, climate change is expected to shorten periods of
snowpack accumulation, as well as reduce snowpack levels. With
gradually increasing temperatures and reduced snowpack (due to higher
spring temperatures and reduced winter-spring precipitation), annual
runoff will be reduced (Smith et al. 2003, p. 226; Ellis et al. 2010,
p. 236), consequently reducing ground water recharge. Second, snowmelt
is expected to occur earlier in the season because increased minimum
winter and spring temperatures could melt snowpacks sooner, causing
peak water flows to occur much sooner than the historical spring and
summer peak flows (Smith et al. 2003, p. 226; Stewart et al. 2005, pp.
217-218, 224, 230) and reducing flows later in the season. Third, the
hydrological cycle is expected to become more dynamic on average with
climate models predicting increases in the variability and intensity of
rainfall events. This will modify disturbance regimes by changing the
magnitude and frequency of floods.
Precipitation events under most climate change scenarios will
decrease in frequency, but increase in severity so that, paradoxically,
a warmer atmosphere and an intensified water cycle are likely to mean
not only a greater likelihood of drought for the Southwest, but also an
increased risk of flooding (Karl et al. 2009, pp. 132-133; Dominguez et
al. 2012, pp. 1-7). Precipitation patterns are already observed to be
shifting in the Southwest, with more rain falling in heavy downpours
that can lead to flooding (Karl et al. 2009, p. 133). Adding to flood
risk is that the earlier streamflow from earlier snowmelt may impinge
on the flood protection stages of reservoir operations so that less
streamflow can be captured safely in key reservoirs, increasing spring
flooding downstream (Smith et al. 2005, p. 1154; Karl et al. 2009, p.
133). In some sites, where natural floodplain dynamics allow for
overbank flooding, this could result in a positive regenerating effect
on habitat for the western yellow-billed cuckoo. However, where
floodplains have been constrained, as in many areas of the range, such
changes in hydrology could excessively scour remaining habitat, thus
preventing their reestablishment and resulting in smaller patch size or
loss of habitat for the western yellow-billed cuckoo. Long drought
cycles could also hamper recruitment of riparian vegetation following
scouring floods and lead to reduced cover and nest sites for the
western yellow-billed cuckoo.
Exactly how climate change will affect precipitation from site to
site within the range of the western yellow-billed cuckoo in the
southwestern United States and northwestern Mexico is uncertain.
However, consistent with recent observations of regional effects of
climate change, the projections presented for the southwest predict
overall warmer, drier, and more drought-like conditions (Hoerling and
Eischeid 2007, p. 19; Seager et al. 2007, p. 1181; Ellis et al. 2010,
p. 243). For example, climate simulations of the Palmer Drought
Severity Index (PSDI) (a calculation of the cumulative effects of
precipitation and temperature on surface moisture balance) for the
Southwest for the periods of 2006 to 2030 and 2035 to 2060 show an
increase in drought severity with surface warming. Additionally,
drought-like conditions will increase even during wetter simulations
because of the effect of heat-related moisture loss through evaporation
and evapotranspiration (Hoerling and Eischeid 2007, p. 19). Annual mean
precipitation is likely to decrease in the Southwest, as is the length
of snow season and snow depth (IPCC 2007b, p. 887; Sun et al. 2013, pp.
21-22). Most models project a widespread decrease in snow depth and
earlier snowmelt in the Rocky Mountains (IPCC 2007b, p. 891).
Assessments for the Sonoran Desert are few, but the region is also
expected to warm (IPCC 2007a, p. 887). Since about the 1970s, the
Sonoran Desert region appears to have experienced ``widespread warming
trends in winter and spring, decreased frequency of freezing
temperatures, lengthening of the freeze-free season, and increased
minimum temperatures per winter year'' (Weiss and Overpeck 2005, p.
2065).
In California, regional downscaled climate change assessments
(Point Reyes Bird Observatory (PRBO) Conservation Science 2011, pp. 1-
68) indicate changes in precipitation and temperature of varying
magnitude across ecoregions. Assessments for areas occupied by the
western yellow-billed cuckoo, such as the Sacramento River, Sierra
Nevada (southern), and Sonora Desert (lower Colorado River) (PRBO
Conservation Science 2011, pp. 25, 28, 48), mostly indicate an overall
reduction in precipitation and increase in average temperature, which
can alter hydrology and negatively affect habitat for the western
yellow-billed cuckoo, as described previously. Furthermore, Gardali et
al. (2012, pp. 8-10) ranked 358 avian taxa in California, and
classified 128 as vulnerable to climate change. They ranked the western
yellow-billed cuckoo as subject to a moderate level of climate
vulnerability, owing in part to its specialization in habitat
(riparian) that has already experienced significant loss or alteration.
Of the 128 species that were rated vulnerable, only 48 were rated as
having high or moderate climate vulnerability.
Regionally downscaled climate models for the Pacific Northwest
project higher air temperatures in the next century (Littell et al.
2009, pp. 6-7) that will lead to lower soil moisture and increased
evaporation from streams and lakes (Climate Leadership Initiative (CLI)
and the National Center for Conservation Science and Policy 2009, p.
8). While high uncertainty exists in the total precipitation
projections for the region (Littell et al. 2009, p. 1), effective
precipitation (precipitation that contributes to runoff) may be reduced
significantly even if there is no decline in total precipitation (CLI
and the National Center for Conservation Science and Policy 2009, p.
8). Increases in extreme high precipitation falling as rain in the
western Cascades and reductions in snowpack are key projections from
high-resolution regional climate models (Littell et al. 2009, p. 1).
These may result in more winter flooding and reduced summer streamflows
in rivers that depend on snowmelt, which include many of the rivers in
the Pacific Northwest.
In drier climates overall, there will be increases in riverine
system temperatures that are predicted to result in periods of
prolonged low flows and stream drying (Stromberg et al. 2013, pp. 411-
415) and increased demand for water storage and conveyance systems
(Stromberg et al. 2013, pp. 411-415). Warmer water temperatures across
temperate regions are likely to increase the density and expand
distribution of tamarisk because it has a higher tolerance for drought
and salt than native cottonwoods and willows (Glenn and Nagler 2005, p.
439). This situation is expected to lead to the conversion of native
and mixed (native and nonnative) riparian habitat to monotypic stands
of tamarisk, which, outside of the Southwest, provides little or no
suitable breeding habitat for the western yellow-
[[Page 61653]]
billed cuckoo (as described previously above).
Increased drought is expected to adversely affect food availability
for western yellow-billed cuckoos (Newton 1980, pp. 11-12; Durst 2004,
pp. 40-41; Scott et al. 2004, p. 70) through the disruption of the
timing between a species and its food resources (Visser and Both 2005,
pp. 2561-2569). For example, changes in precipitation or temperature
may influence the peak timing of insect emergence or timing of the
yellow-billed cuckoo's arrival from its wintering grounds so that the
nesting season does not coincide as closely with peak insect abundance
(Anders and Post 2006, p. 225). This change in timing could result in
reduced food availability for the western yellow-billed cuckoo and
breeding success, possibly causing further population decline and
curtailment of its occupied range.
Virtually all future climate scenarios for the Pacific Northwest
predict increases in wildfire in western North America, especially east
of the Cascades, due to higher summer temperatures, earlier spring
snowmelt, and lower summer flows, which can lead to drought stress in
trees (Littell et al. 2009, p. 14). These effects could result in both
short-term and long-term loss of riparian habitat from excessive winter
scouring, summer drying, and wildfire. Regional downscaled climate
change models for the Intermountain West also provide similar
projections for warmer, drier climate with a reduced snowpack and
episodic precipitation events. Prolonged drought in the southwestern
United States and northern Mexico is expected to increase fire
frequency, which results in a short-term loss of patches of riparian or
thorn forest habitat for breeding. When fire frequency increases,
riparian and thorn forests do not have sufficient time to recover,
resulting in habitat conversion to fire-adapted nonforested vegetation
types unsuitable for nesting. Furthermore, the effects of climate
change and ongoing reduction in habitat and patch fragmentation,
discussed previously, would increase.
Little is known about the wintering habitat of the western yellow-
billed cuckoo in South America, and uncertainty exists about how
climate change will affect it there. Regional downscaled models project
an increase in wet-season precipitation and a decrease in dry-season
precipitation over most of South America (Kitoh et al. 2011, p. 1). In
the future, precipitation intensity will increase over most of South
America. In particular, precipitation intensity will be greatest over
southeast South America, implying an increasing risk of flooding in
this region (Kitoh et al. 2011, p. 1). At the same time, a large
increase of consecutive dry days is projected over the western part of
the Amazon, where extremes in seasonal precipitation and resulting
runoff is projected to increase in the Amazon River, implying more
floods in the wet season and droughts in the dry season (Kitoh et al.
2011, p. 1). Uncertainty exists regarding the specific effects of such
changes on the wintering habitat of the western yellow-billed cuckoo.
In summary, the available climate change models are predicting
altered future environmental conditions across the breeding range of
the western yellow-billed cuckoo. In the southwestern United States,
northern Mexico, California, Intermountain West, and Pacific Northwest,
climate change is generally predicted to result in an overall warmer,
drier climate, with periodic episodic precipitation events that,
depending on site conditions, are expected to have adverse effects on
habitat of the western yellow-billed cuckoo. In rivers that depend on
snowmelt, these changes are expected to result in more winter flooding
and reduced summer stream flows. The amount of surface ground water
available to regenerate and sustain riparian forests is expected to
decline overall with persistent drought, favor the spread of tamarisk
and other nonnative vegetation, and increase fire frequency.
Precipitation events under most climate change scenarios will decrease
in frequency and increase in severity. This change may reduce available
nesting sites, patch size, and affect prey abundance as a result of
lower humidity in riparian areas from reduced moisture retention, and
through periods of prolonged desiccation followed by scouring flood
events. In addition, evidence shows that climate change may disrupt the
synchrony of nesting yellow-billed cuckoos and their food supply,
causing further population decline and curtailment of its occupied
range.
Impacts to habitat from climate change exacerbate impacts from
impoundments, channelization, and alteration of river flows across the
western United States and Mexico, and from conversion of habitat from
native to mostly nonnative vegetation. Changing climate is expected to
place an added stress on the species and its habitats. While we do not
have evidence to suggest that the habitat of the western yellow-billed
cuckoo is being substantially affected by climate change at this time,
we expect long-term climate trends to have an overall negative effect
on the available habitat throughout the breeding range of the western
yellow-billed cuckoo. Moreover, a drying trend associated with global
climate change may result in more dams, levees, or other activities to
ensure fresh water for human consumption, which may result in
additional habitat loss from the activities described in the Habitat
Loss from Dams and Alteration of Hydrology section, above.
Conservation Efforts To Reduce Habitat Destruction, Modification, or
Curtailment of Its Range
A number of beneficial actions with the potential to partially
offset decades of habitat loss and degradation have occurred within the
range of the western yellow-billed cuckoo. These actions include land
acquisition and habitat restoration efforts for the western yellow-
billed cuckoo and its habitat.
Along the Sacramento River and its tributaries in California,
beneficial actions that are hoped to eventually counter some of the
long-term decline of riparian habitat include the acquisition of
approximately 25,000 ac (10,117 ha) of riparian habitat, which has been
preserved by public and private resource conservation entities, mostly
in the past 20 years (Werner 2012, pers. comm.). The Sacramento River
NWR is encompassed in this area and consists of 27 units totaling
10,146 ac along the river between Red Bluff and Princeton (Service
2012, p. 1). Riparian habitat restoration activities have been
conducted on 4,513 ac (1,826 ha) with 2,400 ac (738 ha) slated for
additional restoration (Hammond 2011, p. 14), and is resulting in
larger habitat patch sizes (Werner 2012, pers. comm.). Yellow-billed
cuckoos have been found utilizing these restoration sites as early as 4
years after planting, but the total number observed on the sites is
very low (23 sightings during 2 years of intensive study) (Hammond
2011, pp. 3, 50). Overbank flows have been restored in a small section
of the Sacramento River on the Sacramento River NWR through a small-
scale levee removal project that has resulted in increased riparian
habitat and floodplain function (Silveira 2012, pers. comm.).
Additional riparian habitat is owned and managed by the California
Department of Parks and Recreation (CDPR) (671 ac (272 ha)) and the
California Department of Fish and Wildlife (CDFW) (4,014 ac (1,625
ha)).
Conservation efforts elsewhere in California include the protection
of the Kern River Preserve near Lake Isabella in Kern County, which was
purchased for permanent conservation in 1979 by
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The Nature Conservancy (TNC) and is now managed by Audubon California.
This 2,987-ac (1,209-ha) site has had an active ongoing riparian
habitat restoration program for the past 20 years, and more than 500 ac
(202 ha) have been restored. Livestock grazing has been eliminated or
managed to reduce impacts to riparian habitat for 30 years (Audubon
Kern River Preserve 2012).
In Nevada, Arizona, and other southwestern States, numerous
conservation plans are in various stages of implementation that result
in actions covering thousands of acres of riparian habitat that could
benefit the western yellow-billed cuckoo, as reviewed by the Service
(2010, pp. 5-7). These include, but are not limited to, the Lower
Colorado River Multi-Species Conservation Program (LCRMSCP), which
calls for restoring more than 4,000 ac (1,618 ha) of habitat for the
western yellow-billed cuckoo, various State Wildlife Action Plans, the
Virgin River Habitat Conservation and Recovery Program, Muddy River
Recovery Implementation Program, Warm Spring Natural Area Stewardship
Plan, Horseshoe and Bartlett Reservoirs Habitat Conservation Plan, and
Las Vegas Wash Comprehensive Adaptive Management Plan (Service 2010a,
pp. 5-7).
In Arizona, implementation of the LCRMSCP has successfully
increased occupied western yellow-billed cuckoo habitat through
restoration, and researchers have found greater occupancy of yellow-
billed cuckoos in restored compared to natural habitat along the lower
Colorado River and tributaries (McNeil et al. 2011, pp. 40-41).
Additionally, a number of conservation properties have been purchased
in fee title or as easements since 1996 to offset the effects elsewhere
to southwestern willow flycatchers at Roosevelt Lake and the Salt River
(SRP 2011b, pp. 17-50), and southwestern willow flycatchers and yellow-
billed cuckoos at Horseshoe Reservoir and the Verde River (SRP 2011a,
pp. 25-35). These properties, which also support yellow-billed cuckoos,
include the San Pedro River Preserve, Adobe Preserve, Stillinger
Preserve, Spirit Hollow and Spirit Hollow Annex on the lower San Pedro
River, Camp Verde Riparian Preserve, and the Fort Thomas Preserve on
the Gila River. Other conservation properties along the lower San Pedro
River include Cook's Lake, owned by Reclamation, and Three Links Farm,
with conservation easements held by TNC and Reclamation. Management
actions that have benefitted riparian habitat include retiring water
rights, hiring onsite managers, fencing livestock from streams,
prohibiting off-road vehicles, removing trespass livestock, and
patrolling properties for trespassers and breaks in fences (Sferra
2012, in litt.).
In Arizona, permanent protection of the 6,105-ac (2,472-ha) Bill
Williams River NWR in 1941 conserved one of the best remaining willow-
cottonwood riparian habitat areas on the lower Colorado River, though
it is vulnerable to periodic inundation from Lake Havasu, reduced flows
from Alamo Dam, and an increase in tamarisk. The San Pedro Riparian
National Conservation Area (NCA) encompasses approximately 40 mi (64
km) of the upper San Pedro River meanders. It was designated by
Congress in 1988 with its primary purpose to protect and enhance the
desert riparian ecosystem as an example of what was once an extensive
network of similar riparian systems throughout the American Southwest.
It contains nearly 57,000 ac (23,077 ha) of public land between the
international border with Mexico and St. David, Arizona, and supports
one of the largest western yellow-billed cuckoo populations in Arizona.
However, continually increasing demands for water use within the basin
threatens future flow in the upper San Pedro River. The 2011 District
of Arizona case, Center for Biological Diversity, et al. v. Kenneth
Salazar, et al., CV 07-484-TUC--AWT, ruled that the 2007 plan by the
U.S. Army and U.S. Fish and Wildlife Service failed to protect the
upper San Pedro River or properly analyze Fort Huachuca's ground water
pumping effect on the ecosystem's endangered species and critical
habitat.
In Colorado's San Luis Valley, approximately 1,500 ac (607 ha) of
riparian habitat are under permanent conservation easement along the
Rio Grande and Conejos River, which supports the western yellow-billed
cuckoo. The easements prohibit any activity that alters or diminishes
the value of the wildlife habitat (Service 2011, p. 11). In northern
Mexico, some riparian habitat has regenerated along the lower Colorado
River floodplain in recent years in response to improved hydrological
conditions resulting from binational water agreements, as discussed
previously. During 50 years of reduced flows resulting from extensive
damming of the upper Colorado River in the 1930s, the lower Colorado
River nearly lost its cottonwood-willow forests and was being replaced
by tamarisk (Glenn et al. 2001, pp. 1175-1186; Nagler et al. 2005, pp.
1843-1844). Local loss of the yellow-billed cuckoo and other riparian
birds has been attributed to this habitat loss and degradation,
resulting from decades of limited river flows reaching Mexico. Large-
volume releases of water now reach the floodplain of the lower Colorado
River in Mexico, which has allowed regeneration of limited but vital
stands of native riparian vegetation (Zamora-Arroyo et al. 2001, pp.
49-50; Nagler et al. 2005, pp. 1849-1851; Hinojosa-Huerta et al. 2008,
p. 81). The yellow-billed cuckoo has been regularly detected during
May-July surveys, and is presumably breeding (Hinojoas-Huerta et al.
2008, pp. 80-81).
In northeastern Sonora, Mexico, habitat conservation action
includes the purchase and protection in 2003 of the 10,000-ac (4,046-
ha) Los Pavos-Northern Jaguar Preserve by a nongovernmental
conservation organization. While not managed on the site, yellow-billed
cuckoos were commonly sighted during bird surveys (O'Brien et al. 2008,
p. 1). This rugged roadless area is located on the R[iacute]o Aros,
which is part of the R[iacute]o Yaqui watershed, and is in the core
area that supports one of the largest unfragmented wild areas of
foothills thorn scrub in the State of Sonora (Lorenzana-Pi[ntilde]a et
al. 2004, p. 354). The region surrounding the preserve, however,
remains vulnerable to various new resource extraction activities
(O'Brien et al. 2008, p. 1).
In summary, we believe that conservation actions, such as habitat
protection and restoration, have strong potential to be beneficial to
the species. However, because many of these projects are either in the
planning stages or have not been fully implemented, there is no data to
show that these efforts have reduced or eliminated impacts from ongoing
long-term effects to riparian habitat from the multiple threats of
altered hydrology, livestock grazing, and nonnative vegetation.
Conservation actions that have been implemented have either had
insufficient time in which to demonstrate a population increase or
other factors continue to affect the western yellow-billed cuckoos and
keep abundance low. Even if all of these conservation actions are
successful, they are not of a sufficient magnitude to counter the long-
term decline of the western yellow-billed cuckoo. Impacts to habitat
continue to modify and curtail the occupied range of the western
yellow-billed cuckoo.
Summary of Factor A
We have identified a number of threats to the habitat of the
western yellow-billed cuckoo that have operated in the past, are
impacting the species now, and will continue to impact the
[[Page 61655]]
species in the future. The curtailment and decline in the habitat of
the western yellow-billed cuckoo is primarily the result of the long-
lasting effects of habitat loss from manmade features that alter
watercourse hydrology so that the natural processes that sustained
riparian habitat in western North America are greatly diminished. Loss
and degradation of habitat has also occurred as a result of livestock
overgrazing and encroachment from agriculture. All of these have the
potential to promote, and are exacerbated by, the conversion of native
habitat to predominantly nonnative vegetation. The curtailment,
degradation, fragmentation, and loss of habitat for the western yellow-
billed cuckoo is ongoing and, absent changes in the landscape,
hydrology, or other factors, it will likely continue to be negatively
impacted or lost into the future.
We recognize that climate change is a critical issue with
potentially severe wide-ranging effects on the species and its habitat.
The available scientific literature suggests that the effects of
climate change will likely exacerbate multiple existing threats to the
western yellow-billed cuckoo and its habitat. These threats include
habitat loss and degradation from altered hydrology, with secondary
effects from increases in nonnative vegetation and wildfire. These
threats may result in smaller patch sizes of habitat such that many
will be no longer occupied by the western yellow-billed cuckoo.
Conservation actions, such as habitat protection and restoration
described above, have strong potential to be beneficial to the species
by increasing the amount of available habitat and patch size. However,
these efforts offset only a small portion of past losses and
degradation of riparian habitat in the range of the western yellow-
billed cuckoo. Habitat elsewhere in the range continues to be
vulnerable to loss and degradation from ongoing alterations in
hydrology, nonnative vegetation, and agricultural activities combined
with additional or synergistic effects associated with climate change.
Moreover, we expect these multiple stressors to continue to affect
habitat of the western yellow-billed cuckoo into the future.
Factor B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
There are no known threats to the western yellow-billed cuckoo
resulting from overutilization for commercial, scientific, or
educational purposes. Our review of the best available scientific and
commercial information yielded nothing to indicate that overutilization
for commercial, recreational, scientific, or educational purposes is
occurring at this time or is likely to in the near future in any
portion of the western yellow-billed cuckoo range. We, therefore,
conclude that such overutilization does not currently constitute a
threat to the western yellow-billed cuckoo, nor do we expect it to be a
threat in the future.
Factor C. Disease or Predation
Little is known about diseases in the western yellow-billed cuckoo.
West Nile virus has recently spread throughout portions of the western
United States. It poses a potential threat to many bird species. The
USGS National Wildlife Health Center has identified the yellow-billed
cuckoo as a species that is subject to the effects of West Nile virus
(USGS--National Wildlife Health Center 2005, p. 2). The Center for
Disease Control's Vector-Borne Disease Web site reports that West Nile
virus has been documented in a dead yellow-billed cuckoo (Center for
Disease Control 2012); however, if this yellow-billed cuckoo was from
the western DPS is unknown. Although the population of the western
yellow-billed cuckoo has been in decline over several decades (see
Historical and Current Status section, above), no evidence suggests
that it has undergone a precipitous decline coincident with the
relatively recent arrival of West Nile virus in western North America.
Therefore, we conclude, based on the best available scientific and
commercial information, which is limited, that the adverse effects of
West Nile virus to the western yellow-billed cuckoo are not significant
and do not constitute a threat at this time, nor is there any
information to suggest that this situation will change in the future.
All bird species, including the yellow-billed cuckoo, are exposed,
to some extent, to parasites. Greiner et al. (1975, pp. 1762-1787)
found 5 of 16 yellow-billed cuckoos infected with Leucocytozoon,
Trypanosoma, and microfilaria blood parasites. No information indicates
whether these and other parasites (see Hughes 1999, p. 18, for a brief
review) pose any threat to the western yellow-billed cuckoo.
Predation is a potential threat to the western yellow-billed
cuckoo. On the Kern River, red-shouldered hawks (Buteo lineatus) and
northern harriers (Circus cyaneus) have been observed preying on
nestlings, and yellow-billed cuckoos have been observed chasing western
scrub-jays (Aphelocoma californica) and loggerhead shrikes (Lanius
ludovicianus) away from their nests (Laymon 1998, pp. 12-14); however,
we do not have any information of the frequency of predation. An
inverse relationship appears to exist between the presence of yellow-
billed cuckoos and western scrub-jays on the Sacramento River,
indicating a possible aversion by the yellow-billed cuckoos to nesting
at sites occupied by western scrub-jays, a known predator of eggs and
young (Halterman 1991, p. 38). Cooper's hawks (Accipiter cooperii) are
thought to be the only avian predator capable of taking adult western
yellow-billed cuckoos (Laymon 1998, pp. 12-13), and during migration
adults are susceptible to predation by raptors, such as aplomado
falcons (Falco femoralis) (Hector 1985, p. 338); however, we have no
information to suggest that the rate of adult predation is
significantly affecting the yellow-billed cuckoo population. In the
Sonoran town of Alamos, Mexico, Mackay (David Mackay 2012, in litt.)
witnessed a brown vine snake (Oxybelis aeneus) leaving a yellow-billed
cuckoo nest after eating one of four nestlings.
On the lower Colorado River, McNeil et al. (2011, p. 41) found that
high nest predation rates (63 percent of nests failed) contributed to
the much lower average nest productivity at restoration sites (1.25
young fledged per nest) compared to nests at the Bill Williams River
NWR (2.14 young fledged per nest). Most of that predation was
attributed to avian predators; however, for 2 consecutive years a nest
was preyed upon by a California king snake (Lampropeltis getula
californiae) (McNeil et al. 2011, p. 41; McNeil et al. 2012, p. 50).
Nest predation may have been high in restoration sites because most
were located adjacent to agricultural areas, which may have increased
the exposure of nests to human-adapted avian predators that thrive in
agricultural areas. Additionally, these sites did not yet have the
height, structure, and composition of more complex riparian habitats
(McNeil et al. 2011, pp. 41, 49; McNeil et al. 2012, p. 56) that may
serve to hide nests from predators. Nest predation can be partially
compensated by the ability of yellow-billed cuckoos to renest when a
nest fails. In general, despite the instances of nest predation listed
above, western yellow-billed cuckoos have higher than normal nest
success and lower nest predation rates than other open-cup nesting
birds (Laymon et al. 1997, p. 11).
In summary, western yellow-billed cuckoos, particularly the eggs or
young in nests, are vulnerable to predation. Predation may be a
significant threat in some localities and in some years, and may be
influenced by several factors,
[[Page 61656]]
such as surrounding land use and size and complexity of riparian
habitat. As a result, predation may act periodically in concert with
other stressors that contribute to the decline of the species (which we
discuss in greater detail under Factor E, below). However, we conclude,
that predation by itself does not pose a significant threat to the
western yellow-billed cuckoo at this time, and we do not have any
reason to believe that this will change substantially in the future.
We conclude that predation, parasites, and disease are not
currently significant threats to the western yellow-billed cuckoo, and
are not expected to become significant threats in the near future.
Factor D. The Inadequacy of Existing Regulatory Mechanisms
We have identified a number of significant threats to the western
yellow-billed cuckoo that are impacting the species now and will
continue to impact the species in the future. The decline of the
western yellow-billed cuckoo is primarily the result of the long-
lasting effects of habitat loss and modification from altered hydrology
resulting from decades of dam construction, channelization, water
extraction, and other activities, as well as impacts associated with
climate change. Other threats include loss of habitat to agricultural
and other land uses, overgrazing, exposure to pesticides (which is
addressed in Factor E, below), wildfire, and conversion of habitat to
monotypic stands of nonnative vegetation. Under this factor, we discuss
whether the existing regulatory mechanisms adequately address impacts
to the western yellow-billed cuckoo described under Factors A and E,
based on the best available information.
Federal Regulatory Mechanisms
In the United States, the Migratory Bird Treaty Act (MBTA) (16
U.S.C. 703-712) is the only current Federal protection provided for the
yellow-billed cuckoo. The yellow-billed cuckoo (the entire
taxonomically defined species), which includes the western yellow-
billed cuckoo, is considered a ``migratory bird'' under the MBTA. The
MBTA prohibits ``take'' of any migratory bird. Take is defined as: ``to
pursue, hunt, shoot, wound, kill, trap, capture, or collect, or attempt
to pursue, hunt, shoot, wound, kill, trap, capture, or collect.''
However, no provisions in the MBTA prevent habitat destruction unless
direct mortality or destruction of active nests occurs.
The Federal Land Policy and Management Act of 1976 (FLPMA) (43
U.S.C. 1701 et seq.) requires that ``the public lands be managed in a
manner that will protect the quality of scientific, scenic, historical,
ecological, environmental, air and atmospheric, water resource, and
archeological values; that . . . will preserve and protect certain
public lands in their natural condition; (and) that will provide food
and habitat for fish and wildlife . . . .'' Furthermore, it is the
policy of the Bureau of Land Management (BLM) ``to manage habitat with
emphasis on ecosystems to ensure self-sustaining populations and a
natural abundance and diversity of wildlife, fish, and plant resources
on public lands'' (BLM manual 6500.06). Similarly, the National Forest
Management Act of 1976 (NFMA) directs that the National Forest System
``where appropriate and to the extent practicable, will preserve and
enhance the diversity of plant and animal communities.'' Additionally,
section 219.12(g) calls for the maintenance of viable populations of
native vertebrates in national forests. As such, FLPMA and NFMA have
the potential to benefit the western yellow-billed cuckoo and its
habitat. However, given that the BLM and USFS have discretion in how
these statutes are carried out and measures are implemented, we
continue to see continued loss and degradation of habitat for the
western yellow-billed cuckoo on lands that these agencies manage.
Congress passed the Federal Water Pollution Control Act Amendments
of 1972 and the Clean Water Act (CWA) of 1977 (33 U.S.C. section 1251
et seq.) to provide for the restoration and maintenance of the
chemical, physical, and biological integrity of the Nation's lakes,
streams, and coastal waters. Primary authority for the implementation
and enforcement of the CWA now rests with the U.S. Environmental
Protection Agency (EPA) and, to a lesser extent, the USACE. In addition
to the measures authorized before 1972, the CWA implements a variety of
programs, including Federal effluent limitations and State water
quality standards, permits for the discharge of pollutants and dredged
and fill materials into navigable waters, and enforcement mechanisms.
Section 404 of the CWA is the principal Federal program that regulates
activities affecting the physical integrity of wetlands and other
waters of the United States.
Section 404 prohibits the discharge of dredged or fill material in
jurisdictional waters of the United States, unless permitted by USACE
under section 404(a) (individual permits), 404(e) (general permits), or
unless the discharge is otherwise exempt from regulation as designated
in section 404 (r). Some areas of riparian habitat may be considered
``waters of the United States,'' but many areas of riparian habitat do
not meet the term's strict definition. The Service can review permit
applications and provide recommendations to the USACE to avoid and
minimize impacts and to implement conservation measures for fish and
wildlife resources, including the western yellow-billed cuckoo.
However, incorporation of Service recommendations into section 404
permits is at the discretion of the USACE.
Furthermore, not all activities in wetlands or streams involve
fill, and not all wetlands or streams fall under the jurisdiction of
the USACE. For example, in areas where the historical floodplain has
been cut off from the river by levees, determining the boundaries of
wetlands subject to USACE jurisdiction becomes complex. The areas
behind these levees have had their hydrological characteristics
altered, soil conditions changed, and riparian vegetation removed. As a
result, these former floodplains, which in some cases would be
important to protect and restore as habitat for the western yellow-
billed cuckoo, fall outside the jurisdiction of the USACE.
Additionally, many actions that resulted in adverse hydrological
modifications, such as channelization and levees, were implemented in
compliance with the CWA.
The National Environmental Policy Act (NEPA) (42 U.S.C. 4321 et
seq.) requires all Federal agencies to formally document, consider, and
publicly disclose the environmental impacts of major Federal actions
and management decisions that have significant effects on the human
environment (including natural resources); however, NEPA does not
require that mitigation alternatives be implemented. Additionally, NEPA
applies only to actions by Federal agencies, so private landowners are
not required to comply with NEPA unless a Federal agency is involved
through provision of Federal funding or a Federal permit.
Through the Fish and Wildlife Coordination Act (FWCA) (16 U.S.C.
661 et seq.), the Service may recommend discretionary conservation
measures to avoid, minimize, and offset impacts to fish and wildlife
resources resulting from Federal projects and water development
projects authorized by the USACE and other Federal agencies such as
Reclamation. Therefore, FWCA may provide some protection for the
yellow-billed cuckoo and its habitat through avoidance and
[[Page 61657]]
minimization measures that may be incorporated into Federal projects.
However, these measures are discretionary.
A majority of dams in the western United States supply hydropower,
and their construction and ongoing operation is authorized by the
Federal Energy Regulatory Commission (FERC), under the Federal Power
Act of 1920, which incorporates by reference the FWCA and NEPA. The
remainder of hydropower in the western United States is largely
produced by the USACE and Reclamation. Reclamation also oversees water
diversion and delivery projects. FERC reconsiders its hydropower
licenses every 30 to 50 years. Through the various Federal regulations
under which these agencies implement their water projects, the Service
has an opportunity to periodically review their permits and relicensing
applications and provide its recommendations to avoid and minimize
impacts, and implement conservation measures for fish and wildlife
resources, including species such as the western yellow-billed cuckoo.
Implementation of these recommendations by FERC, USACE, and Reclamation
is discretionary for nonlisted species. We continue to see loss and
degradation of habitat for the yellow-billed cuckoo as a result of
altered hydrology from operation of dams and other water supply
projects, as described under Factor A.
The EPA is responsible for regulating pesticides under the Federal
Insecticide, Fungicide, and Rodenticide Act and the Food Quality
Protection Act. Before a pesticide can be distributed, sold, and used
in the United States it must first go through a registration process
through the EPA. The EPA conducts short- and long-term toxicity tests
to evaluate potential adverse effects on humans, wildlife, fish, and
plants, including endangered species and nontarget organisms, and
evaluates the potential for possible contamination of surface water or
ground water from leaching, runoff, and spray drift. The sensitivity of
any life stages of the yellow-billed cuckoo or its prey items to
exposure from common agricultural pesticides that could leach, runoff,
or migrate from agricultural areas into the habitat of the yellow-
billed cuckoo has not been tested. However the EPA does conduct
evaluation on these factors on surrogate species and has determined the
use of certain approved pesticides are appropriate in areas used by the
western yellow-billed cuckoo. Even if approved application procedures
are followed, pesticides could reduce available insect prey for the
western yellow-billed cuckoos.
State Regulatory Mechanisms
The majority of occupied areas for the western yellow-billed cuckoo
north of Mexico occur within California, Arizona, and New Mexico
(Hughes 1999, p. 1). Only California classifies the yellow-billed
cuckoo as endangered (CDFW 2011, p. 10). The California Endangered
Species Act (CESA) prohibits unpermitted possession, purchase, sale, or
take of listed species. However, the CESA definition of take does not
include harm, which under the Federal Act can include destruction of
habitat that actually kills or injures wildlife by significantly
impairing essential behavioral patterns (50 CFR 17.3). CESA does
require consultation between the CDFW and other State agencies to
ensure that their activities will not jeopardize the continued
existence of State-listed species; however, the yellow-billed cuckoo
continues to decline in California despite its status as a State-listed
species. In Arizona, the yellow-billed cuckoo is listed as a species of
concern (Arizona Game and Fish Department 2002, p. 3), with no
protective status. The yellow-billed cuckoo has no special protective
status in New Mexico.
Washington State's Department of Fish and Wildlife considers the
yellow-billed cuckoo a candidate for listing. The State wildlife
agencies in Wyoming, Montana, Colorado, Utah, and Texas classify the
yellow-billed cuckoo as a species of concern or a sensitive species.
The yellow-billed cuckoo is identified as a Species of Greatest
Conservation Need in Idaho's Comprehensive Wildlife Conservation
Strategy (Idaho Department of Fish and Game 2005, Appendix B, p. 7),
and, under Idaho State law, is considered a protected nongame species
for which it is illegal to intentionally take or possess, except as
provided in sections 36-106(e) and 36-1107, Idaho Code, by Commission
rule, or the Idaho Administrative Procedures Act 13.01.10, ``Rules
Governing the Importation, Possession, Release, Sale, or Salvage of
Wildlife,'' subsection 100.06.b (Idaho Department of Fish and Game
2005, Appendix B, p. 5). While protected status extends certain
protections to the yellow-billed cuckoo in Idaho, neither this status
nor the Species of Greatest Conservation Need designation protects its
habitat. In Nevada, the yellow-billed cuckoo is identified as
critically imperiled due to extreme rarity, imminent threats, or
biological factors, but this designation provides no protection for
habitat. Yellow-billed cuckoos have no State status in Oregon because
it has not been considered an active breeding species since the 1940s
(Oregon Department of Fish and Wildlife 2005, p. 3). State Wildlife
Action Plans that include the yellow-billed cuckoo as a species of
conservation concern are: California, Washington, Arizona, Colorado,
Montana, Idaho, New Mexico, Utah, Texas, Nevada, and Wyoming. These
plans identify conservation needs and actions for a broad range of
species and habitats, but their implementation is discretionary.
In summary, where the yellow-billed cuckoo is State-listed (CA), a
State candidate (WA), a species of concern or sensitive species (AZ,
ID, WY, MT, CO, TX), or critically imperiled (NV), these designations
contain no protection for the western yellow-billed cuckoo from habitat
modification or destruction, as described under Factors A and E.
Existing State regulatory mechanisms have not protected the western
yellow-billed cuckoo from habitat loss and degradation from altered
hydrology from upstream dams and surface water and ground water
diversions, encroachment into the floodplain by agricultural and other
development activities, bank stabilization and levee construction and
maintenance activities, overgrazing, pesticide use on adjacent
agricultural lands, conversion of habitat to monotypic stands of
nonnative vegetation, gravel mining, wildfire, drought, and climate
change across the range of the western yellow-billed cuckoo.
Canadian, Mexican, and other International Laws
Canada
The Canadian Government through the Department of the Environment
(Environment Canada, which was first established by the Department of
the Environment Act of 1971) administers numerous acts to preserve and
enhance the quality of Canada's natural environment. Acts identified
for conservation of wildlife and plant species or their habitat are
identified below.
1916 Great Britain-United States Convention for the Protection of
Migratory Birds. Canada has committed to migratory bird protection
through the 1916 Great Britain-United States Convention for the
Protection of Migratory Birds in Canada, which encourages voluntary
cooperative actions to protect identified migratory birds. The yellow-
billed cuckoo is listed under the 1916 Great Britain-United States
Convention for the Protection of Migratory Birds in Canada. In
addition,
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Canada has enacted the Migratory Birds Convention Act of 1994 (MBCA).
The MBCA is intended to ensure the conservation of migratory bird
populations by regulating potentially harmful human activities. The
implementing regulations of the MBCA ban all activities that are
harmful to migratory birds, their eggs or their nests, but does not
protect habitat. Also, some activities, such as hunting or scientific
collection may be allowed with an appropriate permit.
The Species at Risk Act of 2002. The purpose of the Species at Risk
Act (SARA) is to prevent Canadian native wildlife and plant species,
subspecies, and distinct populations from becoming extirpated or
extinct, to provide for the recovery of endangered or threatened
species, and encourage the management of other species to prevent them
from becoming at risk. SARA, establishes the Committee on the Status of
Endangered Wildlife in Canada (COSEWIC) as an independent body of
experts responsible for assessing and identifying species at risk. SARA
also, among other objectives, establishes: prohibitions to protect
listed Canadian threatened and endangered species and their critical
habitat; requirements for use of the best available knowledge on
assessing threats to and conservation for wildlife and plant species;
and long- and short-term objectives for development of recovery
strategies and action plans.
The yellow-billed cuckoo is not identified as a species that is
sensitive, threatened, or endangered under Canadian law. Within the
range of the western yellow-billed cuckoo, British Columbia considers
the yellow-billed cuckoo as an extirpated breeder, but that the species
still does occur within the Province (British Columbia Conservation
Data Centre, 2013).
Canadian Environmental Protection Act of 1999. The Canadian
Environmental Protection Act sets out several guiding principles for
conserving the environment including but not limited to supporting:
Sustainable development; pollution prevention; elimination of releases
of substances that are persistent or that bioaccumulate; an ecosystem
approach and using the precautionary principle on issues related to the
environment; science-based national standards; and seeking
intergovernmental cooperation for consistency and avoidance of
duplication of efforts. Because the yellow-billed cuckoo is not
considered a species at risk, implementation of environmental
protection regulations are optional for the species.
Mexico
The Mexican Government, through its Secretaria de Medio Ambiente y
Recursos Naturales (SEMARNAT), has authority to designate species as
threatened or endangered. The western yellow-billed cuckoo is not
listed by the Mexican Government's Official Mexican Norm NOM-059-
SEMARNAT-2010, Mexico's threatened species law. The yellow-billed
cuckoo is listed under the 1936 Mexico-United States Convention for the
Protection of Migratory Birds and Game Mammals (Service 2012b), which
encourages voluntary cooperative actions to protect identified
migratory birds and mammals.
In 1988, the Mexican Government passed the General Law of
Ecological Equilibrium and Environmental Protection, which is similar
to NEPA in the United States. This Mexican statute requires an
environmental assessment of private or government actions that may
affect wildlife or their habitat. Currently, no known regulatory
mechanisms or conservation planning is in place that specifically
targets the conservation of yellow-billed cuckoo habitat within the
range of the DPS in Mexico. Therefore, we anticipate continued threats
in Mexico, with little or no protection to the western yellow-billed
cuckoo.
The National Natural Protected Areas (NPAs) system is a Mexican
program to protect sensitive habitats and species. NPA designation is
supposed to protect areas that have not been significantly altered by
human activities and that provide diverse ecosystem services. However,
prior to 1994, most NPAs lacked sound and comprehensive management
plans. By 2000, approximately 30 percent of new and existing NPAs had
developed management plans; however, under the NPA model these plans
lacked detailed information, and in many cases could be considered
obsolete. NPA goals to promote sustainable natural resources are often
unattainable because of conflicting land ownership interests (Valdez et
al. 2006, p. 272). The allocation of funds for management of natural
reserve areas in Sonora is not assured, and some reserves have not
received protection other than that given by government edicts or their
natural isolation (Burquez and Martinez-Yrizar 1997, p. 378). Urban
development has reduced some of Sonora's natural reserves. Three of the
reserves have already disappeared, reflecting the tenuous state of many
nature reserves in Mexico (Burquez and Martinez-Yrizar 2007, p. 546).
Wildlife management units, or UMAs, were part of a program
developed and implemented by SEMARANT in 1997 to promote wildlife
management on private property in Mexico (Weber et al. 2006, p. 1480).
The UMA program has not been effective in promoting wildlife management
or biodiversity conservation. It has increased the introduction of
exotic wildlife species to meet hunting demands. There is a lack of
technical capability on private lands to conduct proper wildlife
monitoring and management (Weber et al. 2006, p. 1482). In Mexico, the
exploitation of minerals and industrial development has not been
matched by strong measures to protect the environment (Burquez and
Martinez-Yrizar 2007, p. 547). Surface water and ground water
management in Mexico is also lacking, and restoring water quality and
quantity to water bodies is a primary concern (OECD 2013, p. 102). In
the State of Sonora, 30 years of unregulated water extraction from both
above and below ground has resulted in serious water resource
overexploitation and degradation (OECD 2013, p. 115). Although
regulatory measures are in place, they lack consistent implementation
and oversight (OECD 2013, p. 133).
Current efforts for protecting the western yellow-billed cuckoo in
Mexico primarily consist of Important Areas for Bird Conservation
([Aacute]reas de Importancia para la Conservaci[oacute]n de las Aves),
but no specific projects or conservation efforts are focused on the
yellow-billed cuckoo (S[aacute]nchez-Gonz[aacute]lez and Berlanga 2012
in litt.).
Lack of habitat protection for the yellow-billed cuckoo in
northwestern Mexico also impacts the western yellow-billed cuckoo in
the United States because individuals are known to make transitory
movements up to several hundred miles between the southwestern United
States and northern Mexico within a single breeding season (Sechrist et
al. 2012, p. 5), so that individuals that breed in the United States
also depend to some extent on habitat in northern Mexico. No known
information is known on the number of yellow-billed cuckoos that
utilize habitats in both countries during a given breeding season;
however, these are also stopovers areas between breeding and wintering
grounds in South America, and are important as foraging habitat.
Therefore, lack of regulatory protections for habitat of the yellow-
billed cuckoos in northwestern Mexico also affects western yellow-
billed cuckoos in the southwestern United States.
[[Page 61659]]
In regard to potential for pesticide exposure south of the United
States border, Mexico has the second largest pesticide sales in Latin
America, behind Brazil, which together account for 78 percent of the
volume of pesticides within 11 Latin American countries (Mora 1997, pp.
3-4). While Mexico has laws concerning pesticide use, and import
regulations on certain pesticides, there is limited enforcement
capacity (Behre 2003, pp. 337-338). The same is true in Paraguay,
Bolivia, Brazil, and Argentina where yellow-billed cuckoos winter. For
example, in Paraguay, at the center of the yellow-billed cuckoo's
wintering range, importation and use of many pesticides are banned, but
it is estimated that the amount of pesticides that are imported
illegally are double the amount that are imported legally (Scribano
2013).- For additional information on pesticides see Factor E below.
Based on the best available information, the regulatory mechanisms
in Mexico that would protect the western yellow-billed cuckoo from
threats described under Factors A and E are either lacking or not being
fully implemented. These include water supply projects, water
diversions, expansion of agricultural activities and overgrazing,
conversion of habitat to nonnative vegetation, climate change (Factor
A), and pesticides, as well as the threat of small, isolated patches of
western yellow-billed cuckoo habitat (Factor E).
Summary of Factor D
Various Federal, State, and international regulatory mechanisms in
place provide varying degrees of conservation oversight that may to
some degree address the threat of ongoing habitat loss and degradation
resulting from altered hydrology, conversion of habitat to nonnative
vegetation, climate change, agricultural activities (Factor A), or
exposure to pesticides and effects of small and isolated habitat
patches (Factor E). In California, where the species is listed as
endangered, regulations prohibit unpermitted possession, purchase,
sale, or take of listed species. Such prohibition of take does not
include the species habitat, and the yellow-billed cuckoo continues to
decline in California despite its status as a State-listed species.
However, because the yellow-billed cuckoo is not a protected or
sensitive species in Canada, Mexico, or in a majority of the United
States, application of these regulatory mechanisms to conserve yellow-
billed cuckoo or its habitat is unknown and the effectiveness of these
regulatory mechanisms is uncertain.
Factor E. Other Natural or Manmade Factors Affecting Its Continued
Existence
Small and Widely Separated Habitat Patches
As described in the Background section and under Factor A, the
habitat of the western yellow-billed cuckoo has undergone significant
loss and modification within its occupied breeding range as a result of
widespread multiple human-caused effects. These include altered
hydrology in watercourses and past loss and degradation from
agriculture. Past destruction and modification transformed formerly
large expanses of riparian habitat into a number of smaller patches of
smaller total area, isolated from each other by a matrix of mostly
human-altered habitats (McGill, 1975, pp. 1-4; Thompson, 1961, pp. 294-
315; Wilcove et al. 1986, p. 237). As a result, the DPS now primarily
occurs in smaller, more widely separated populations. Compared to large
populations, smaller populations are disproportionately affected by
natural and manmade factors. These stressors vary in frequency, timing,
and magnitude across the species' range. They are related or correlated
to each other or act in combination to result in significant impacts to
the western yellow-billed cuckoo within all or portions of its range.
One of the ramifications of smaller, more isolated habitat patches
is that the smaller the patch, the more edge it has in proportion to
its area, which increases the percentage of the available habitat
exposed to the surrounding land uses (Hunter 1996, pp. 186-187). This
is a particularly prevalent characteristic of the yellow-billed
cuckoo's remaining disjunct habitat patches, as many patches are in
proximity to agricultural and other human-altered landscapes. For
example, such land use currently dominates much of the riparian
landscape within many regions, particularly along some reaches of the
lower Colorado River, Sacramento River, Snake River, Verde River, Gila
River, Santa Cruz River, San Pedro River, and R[iacute]o Grande; and
also in parts of northern Mexico in the vicinity of floodplain farming
along the Sonora, Magdalena, and Moctezuma Rivers (Villase[ntilde]or-
Gomez 2006, p. 111).
Agricultural activities on adjacent lands affect riparian bird
communities in ways that may result in lower reproductive success, and
possible abandonment of the patch, as reviewed by Saab (1999, pp. 136,
147-148). Saab (1999, p. 147) found that bird species, including the
yellow-billed cuckoo, were more likely to occur in riparian habitat
along the Snake River, Idaho, in sites surrounded by upland natural
vegetation than in habitat adjacent to agricultural lands. Saab found
that, compared to habitat patches surrounded by natural habitat,
patches near agricultural lands supported more avian nest predators
that prosper in human-altered landscapes and have a greater effect on
the smaller, fragmented habitats (Saab 1999, p. 147). Increases in
these predators can result in more nest losses and discourage yellow-
billed cuckoos from nesting, thus suppressing local yellow-billed
cuckoo population size. Increases in nonnative vegetation can displace
or degrade suitable nesting and foraging habitat, thereby leading to
lower utilization of such areas by western yellow-billed cuckoos.
Together, the effects can lead to yellow-billed cuckoos abandoning
these small habitat patches.
The western yellow-billed cuckoo is currently found in the largest
contiguous and least-fragmented remaining habitat patches. For example,
in California, sites larger than 198 ac (80 ha) in extent and wider
than 950 ft (600 m) provided optimal patch size for yellow-billed
cuckoos (Laymon and Halterman 1989, p. 275). Nesting yellow-billed
cuckoos are sensitive to patch size and seldom use patches smaller than
325 x 975 ft (100 x 300 m) (Hughes 1999, p. 20). This observed
preferential use of large patches strongly suggests that the DPS is
sensitive to fragmentation and reductions in habitat patch size.
Moreover, patch-size reduction combined with the scarcity of larger
patches keeps the yellow-billed cuckoo breeding population size
depressed. Such effects prevent the western yellow-billed cuckoo from
reversing its long-term decline in population and range (Hunter 1996,
pp. 179-187).
Moreover, isolated breeding sites separated by hundreds of miles of
nonhabitat also reduce the ease with which dispersing juvenile and
returning adult yellow-billed cuckoos are able to find these sites.
This isolation may result in low colonization and re-occupation rates,
so that otherwise suitable habitat remains unoccupied or occupied at
low densities (Laymon and Halterman 1989, p. 274; Hunter 1996, p. 185).
For example, the Sacramento River still appears to have sufficient
habitat to maintain a self-sustaining population of yellow-billed
cuckoos, as over 25,000 ac (10,117 ha) of riparian and associated
natural habitat has been protected and other sections are in the
process of being restored. However, not all suitable patches are
occupied or may only be
[[Page 61660]]
occupied in very low densities, and the yellow-billed cuckoo population
remains much lower than its potential (Dettling and Howell 2011, pp.
20-21).
In summary, despite efforts to protect and restore riparian habitat
along the Sacramento River and elsewhere in the range of the western
yellow-billed cuckoo, these efforts offset only a small fraction of
historical habitat that has been lost. Therefore, the threats resulting
from the species' behavioral response to the multiple, combined effects
of small and widely separated habitat patches exacerbate the effect of
other threats within a large portion of the range of the western
yellow-billed cuckoo. Moreover, because the threats that create small
and isolated patches are ongoing (see Factor A), we expect the effects
of the species' response to small patch size to continue to adversely
impact the western yellow-billed cuckoo into the future.
Pesticides
Exposure to pesticides may also be a threat to western yellow-
billed cuckoos because it negatively impacts populations of insect prey
(Groschupf 1987, p. 29; Hughes 1999, p. 2). The effects of pesticides
on western yellow-billed cuckoos can be from intentional aerial
spraying of habitat for mosquito or forest pest control, or from
overspray when foraging habitat is located next to agricultural fields.
Prey populations were affected by aerial spraying of larvicides for
control of mosquitoes at Caswell State Park in California (Laymon 1998,
p. 12) and in Colorado to control an outbreak of caterpillars on box
elders near Durango (Colyer 2001, pp. 1-6). The available evidence
suggests that a reduction in prey availability results in reduced
nesting success (Laymon 1980, p. 27; Hughes 1999, pp. 19-20), and pairs
may even forgo breeding in years with inadequate food supplies (Veit
and Petersen 1993, pp. 258-259). Therefore, the application of
pesticides directly onto areas of riparian habitat may indirectly
affect the reproductive success of the western yellow-billed cuckoo,
leading to nest failure and lowered population size. Additionally,
because breeding site fidelity is in part dependent on previous
successful nesting (see the Breeding Site Fidelity section), yellow-
billed cuckoos may abandon otherwise suitable nest sites where prey
availability is limited by pesticide use, resulting in curtailment of
its occupied range.
Effects from overspray of pesticides are more pronounced in smaller
patches next to agricultural fields (because they have more edges,
which allows for increased chances of exposure) but the effects of
pesticides could also affect larger habitat patches as well. In areas
where riparian habitat borders agricultural lands, such as California's
Central Valley, the lower Colorado River, Snake River, Gila River,
R[iacute]o Grande Valley, and rivers in northern Mexico, including the
Sonora, Yaqui, Mayo, and Moctezuma, pesticide use indirectly affects
western yellow-billed cuckoos by reducing prey numbers, or by poisoning
nestlings if sprayed directly in areas where the birds are nesting
(Laymon and Halterman 1987b, p. 23; Lehman and Walker 2001, p. 12).
Accumulation of chlorinated hydrocarbon pesticides, particularly
dichlorodiphenyltrichloroethane (DDT), has affected other bird species,
particularly top predators (Robinson and Bolen 1989, pp. 269-275).
Pesticides may affect behavior (for example, loss of balance) or cause
death by direct contact. Laymon (1980, pp. 11-12) reported sublethal
poisoning of young yellow-billed cuckoos caused by spraying active
nests in walnut orchards in California.
Although DDT use has been banned in the United States since 1972,
and in Mexico since 1999, yellow-billed cuckoos may be exposed to DDT
in Mexico or on wintering grounds where DDT is still used despite any
bans on its use. For example, yellow-billed cuckoos (most likely of the
eastern population) collected during the spring and fall migration in
Florida had unusually high concentrations of DDT, suggesting exposure
on the wintering grounds in South America (Grocki and Johnston 1974,
pp. 186-188). Analysis of two eggs collected in California in 1979
showed very low levels of dichlorodiphenyldichloroethylene (DDE), a
stable metabolite of DDT, but eggshell fragments collected in 1985 from
three nests along the South Fork Kern River in California averaged 19
percent thinner than pre-DDT era eggshells (Laymon and Halterman 1987b,
pp. 22-23). DDT has caused eggshell thinning in other bird species, and
this percentage of thinning in other species has allowed eggs to be
crushed during incubation, but there is no information showing that
yellow-billed cuckoo eggs have been crushed during incubation because
of shell thinning.
A recent study in southern Sonora, Mexico, tested for the presence
of a group of agricultural pesticides banned in the United States,
known as organochlorine pesticides (beta-hexachlorocyclohexane (BHC),
lindane, aldrin, endrin, b-endosulfan, methoxychlor, p, p0-DDE, p, p0-
Dichlorodiphenyldichloroethane (DDD), p, p0-DDT). Collectively called
OCPs, these pesticides are persistent in the environment and,
therefore, have the potential to move long distances in surface runoff
or ground water. Soil samples collected from 24 localities in the Yaqui
and Mayo Valleys of southern Sonora, Mexico, watersheds in which the
western yellow-billed cuckoo is known to breed, were found to have
higher OCP levels than other regions of the world. The OCPs were
predominantly DDT (Cantu-Soto et al. 2011, p. 559), despite its having
been discontinued in Mexico in 1999 after decades of heavy use in
agriculture and for malaria control (Ya[ntilde]ez et al. 2004, p. 18).
This finding may indicate recent applications of DDT in agricultural
soils (Cantu-Soto et al. 2011, p. 559). Because of the proximity of
habitat for yellow-billed cuckoos to these valleys and the prevalence
of floodplain agriculture in northern Mexico, these pesticides,
especially DDT, may be having widespread long-lasting effects on the
western yellow-billed cuckoo. These include direct and indirect
exposure through ingestion of contaminated prey items, and reduction in
prey availability from direct exposure and pesticide runoff into
habitat that supports western yellow-billed cuckoos.
In summary, pesticide use is widespread in agricultural areas in
the western yellow-billed cuckoo breeding range in the United States
and northern Mexico. Yellow-billed cuckoos are exposed to the effects
of pesticides on their wintering grounds, as evidenced by DDT found in
their eggs and eggshell thinning in the United States. Because much of
the species' habitat is in proximity to agriculture, the potential
exists for direct and indirect effects to a large portion of the
species in these areas through altered physiological functioning, prey
availability, and therefore, reproductive success, which ultimately
results in lower population abundance and curtailment of the occupied
range. While agricultural pesticides can kill prey of the yellow-billed
cuckoo, and documentation exists of pesticide exposure in the wild,
described above, no known data is available to determine specifically
how often agricultural chemicals are affecting yellow-billed cuckoo
prey availability, locations where it may be particularly significant,
or the extent to which pesticides are responsible for population-level
effects in the western yellow-billed cuckoo. However, based on the
close proximity of agricultural areas to where the western yellow-
billed cuckoo breeds, the threat is potentially significant.
[[Page 61661]]
Collisions With Communication Towers and Other Tall Structures
Yellow-billed cuckoos are vulnerable to collision with
communication towers and other tall structures, particularly during
their migration. For example, several hundred yellow-billed cuckoo
mortalities were documented at a single television tower in Florida
over a 29-year period (Crawford and Stevenson 1984, p. 199; Crawford
and Engstrom 2001, p. 383), and at an airport ceilometer in the east
(Howell et al. 1954, p. 212). Lesser numbers of yellow-billed cuckoos
have been reported as killed at other sites with both television towers
and wind turbines in Wisconsin, West Virginia, and northern Texas
(Kemper 1996, p. 223; Schechter 2009, p. 1; Bird Watching 2011, p. 1),
Although these mortalities were in the eastern segment of the
population, with the number of tall towers that have been constructed
in recent years in western United States, the potential exists for
collisions with the western yellow-billed cuckoo. Without further
study, we anticipate this to be a minor, but ongoing, effect to
individual yellow-billed cuckoos, but in combination with all the other
effects to this species, as described under Factors A and E, mortality
from collision would have an additive effect to the threats facing the
western yellow-billed cuckoo.
Conservation Efforts To Reduce Other Natural or Manmade Factors
Affecting Its Continued Existence
Restoration of riparian habitat on the Colorado, Kern, and
Sacramento Rivers and elsewhere will help reduce habitat fragmentation,
small patch size, and overall lack of habitat. In some restoration
plans, reduction of fragmentation is a stated goal, and restoration
sites are planned for sites adjacent to existing habitat. The Colorado
River riparian habitat restoration work is just beginning and is part
of the Lower Colorado River Multi-Species Conservation Plan. This
habitat conservation plan call for the creation of 5,940 ac (2405 ha)
of riparian habitat of which 4,050 ac (1,640 ha) will be suitable for
western yellow-billed cuckoos (Reclamation 2012, pp. 1-3). Restoration
work began on the South Fork Kern River in California, in 1986. To
date, 340 ac (138 ha) of riparian habitat have been restored (Audubon
California 2012, pp. 1-10). Along the Sacramento River, the Sacramento
River National Wildlife Refuge has implemented a riparian restoration
program. Riparian habitat restoration activities have been conducted on
4,513 ac (1,826 ha) with 2,400 ac (738 ha) slated for additional
restoration (Hammond 2011, p. 14). At present, restoration is being
done on a relatively small scale in comparison to the need to reduce
habitat fragmentation and increase the overall extent of suitable
habitat.
DDT has been banned in the United States for several decades, which
reduces the exposure of yellow-billed cuckoos to this pesticide.
However, use of DDT south of the border in Central and South America
continues, and the yellow-billed cuckoos are exposed during migration
and winter.
To date, conservation efforts, though helpful, have been inadequate
to significantly reduce the effects of these other natural or manmade
factors affecting the western yellow-billed cuckoo.
Summary of Factor E
As noted in Factor A, habitat for the western yellow-billed cuckoo
has been modified and curtailed, resulting in only remnants of formerly
large tracts of native riparian forests, many of which are no longer
occupied by western yellow-billed cuckoos. Despite recent efforts to
protect existing, and restore additional, riparian habitat in the
Sacramento, Kern, and Colorado Rivers, and other rivers in the range of
the western yellow-billed cuckoo, these efforts offset only a small
fraction of historical habitat that has been lost. Therefore, we expect
the threat resulting from the combined effects associated with small
and widely separated habitat patches to continue to affect a large
portion of the range of the western yellow-billed cuckoo. This threat
is particularly persistent where small habitat patches are in proximity
to human-altered landscapes, such as near agricultural fields that
dominate the landscape in many areas where the western yellow-billed
cuckoo occurs. As a result, the potential exists for pesticides to
directly affect (poisoning individual cuckoos) and indirectly affect
(reducing the prey base) a large portion of the species. These effects
could ultimately result in lower population abundance and curtailment
of its occupied range. Mortality from collisions with tall structures
is also an ongoing, but largely unquantified effect.
Effects From Factors A through E in Combination
Habitat loss and degradation occurs throughout the range of the
western yellow-billed cuckoo (see Background section and Factor A
above), and many of the threats under Factor A have worked and are
working in combination to reduce the amount, configuration, and quality
of the riparian habitat that remains. To provide a generalized example,
the following scenario is not atypical for much of the species' range:
Installation of a dam along a watercourse allows for increased
agricultural and urban development downstream of the dam because of the
reduced risk of flooding and increased assurance of available water for
human uses. This development, as it expands through time, results in
increased channelization of the watercourse and increased ground and
surface water extraction. These activities affect the watercourse's
hydrological regime and natural hydrologic functioning such that,
through reduced flooding, changes in the watercourse's channel, and a
lowered water table, the native riparian vegetation becomes stressed,
woody debris accumulates, and few new native plants grow. This
situation then allows for increased intensity and extent of wildfires
(which, in riparian areas, often has a human ignition source, another
indirect effect of development) and favors conditions that encourages
the growth of nonnative plants. All of these actions result in a
continued loss and degradation of native riparian vegetation, which
occurs as smaller, more isolated (fragmented) patches that are less
likely to adequately provide for the needs of the western yellow-billed
cuckoo.
This array of Factor A threats, working in combination, creates the
situation that then allows threats from the other listing factors to
markedly affect the species. These other-factor threats may not be
significant in and of themselves, but because they are not occurring in
isolation they, in combination, are contributing to the population
decline of the species. For example, as discussed in the Small and
Widely Separated Habitat Patches section of Factor E, above, small
habitat patches (resulting from the effects of Factor A threats) are
more likely to have a larger number and a wider range of nest predators
(see the Predation section of Factor C, above) because more nest
predators occur in ecological edges. Additionally, habitat patches near
areas of agricultural or urban development can foster higher densities
of potential nest predators. Thus, any western yellow-billed cuckoo
nesting in a small habitat patch near development may be subject to
higher levels of nest predation and thus lower productivity. Moreover,
the mere presence of certain nest predators in a habitat patch may
elicit a behavioral response from yellow-billed cuckoos such that they
do not even attempt to nest in such habitat
[[Page 61662]]
patches, even if other aspects of the habitat would suggest that it is
suitable for nesting.
Similarly, riparian habitat patches that occur near urban and
agricultural development may be subject to intentional or accidental
pesticide spraying, as discussed in the Pesticide section under Factor
E. This spraying would be unlikely to occur but for the habitat patch's
proximity to development. This development likely occurs close to the
riparian habitat through a process similar to the generalized scenario
described above (see also specific details under Factor A).
Much of the available habitat is now in small patches with only a
relatively few patches regularly occupied by nesting western yellow-
billed cuckoos. Thus, the species' intolerance of small patch size in
combination with extensive habitat loss has resulted in much less
suitable habitat and a greatly reduced western yellow-billed cuckoo
population size. In areas at the edge of the western yellow-billed
cuckoo's current range (e.g. the Sacramento River) restoration of
riparian habitat has not been accompanied by an increase in the
species' population indicating that other factors may be limiting the
population in those areas. Moreover, because (1) western yellow-billed
cuckoos need riparian habitat in a range of ages, including older, more
structurally diverse areas for nesting, and (2) nearly all of the areas
where riparian habitat could grow in western North America are modified
by dams, channelization, water extraction, and other activities that
disrupt natural processes to allow good-quality riparian habitat to
grow in a mosaic of different ages (see Factor A), and climate change
is likely to further add to these impacts, it is unlikely that large
areas of suitable habitat will naturally regenerate within the range of
the species into the future.
Proposed Determination
We have carefully assessed the best scientific and commercial data
available regarding the past, present, and reasonably anticipated
future threats to the western yellow-billed cuckoo. Threats to the
western yellow-billed cuckoo exist for two of five threat factors.
Threats also occur in combination, resulting in synergistically greater
effects.
Factor A threats result from habitat destruction, modification, and
degradation from dam construction and operations, water diversions,
riverflow management; stream channelization and stabilization;
conversion to agricultural uses, such as crops and livestock grazing;
urban and transportation infrastructure; and increased incidence of
wildfire. Continuing ramifications of actions that caused habitat loss
in the past have resulted in ongoing curtailment of the habitat of the
yellow-billed cuckoo western DPS throughout its range. These factors
also contribute to fragmentation and promote conversion to nonnative
plant species, particularly tamarisk. The threats affecting western
yellow-billed cuckoo habitat are ongoing and significant and have
resulted in curtailment of the range of the species. Loss of riparian
habitat leads not only to a direct reduction in yellow-billed cuckoo
numbers but also leaves a highly fragmented landscape, which in
combination with other threats (see below), can reduce breeding success
through increased predation rates and barriers to dispersal by juvenile
and adult yellow-billed cuckoos.
Factor E threats, including habitat rarity and small and isolated
population sizes cause the remaining yellow-billed cuckoo populations
to be increasingly susceptible to further declines through lack of
immigration, reduced populations of prey species (food items),
pesticides, and collisions with tall vertical structures during
migration. The serious and ongoing threat of small overall population
size, which is the result of other threats in combination, leads to an
increased chance of local extirpations.
The threats that affect the western yellow-billed cuckoo are
important on a threat-by-threat basis, but are even more significant in
combination. Habitat loss has been extensive throughout the range of
the western yellow-billed cuckoo. The remaining riparian habitat is
fragmented into small patches, which the species does not normally
select as breeding habitat. Additionally, the western yellow-billed
cuckoos need riparian habitat in a range of ages, including older
structurally diverse areas for nesting. This diversity of tree ages
within the riparian vegetation (the DPS's habitat) is largely dependent
on disturbances that affect some but not all of vegetation within that
habitat patch at one time. A number of threats, working in combination
or individually, prevent this from happening, now and will continue to
do so in the future.
For example, dams and other flood control modifications to a
watercourse may prevent floods from being severe enough to affect that
habitat patch; channelization may restrict floodwaters to a narrow
channel, allowing floodwaters to cause too much damage to habitat
within the channel and not enough (or no) damage to habitat outside the
channel; altered flood regimes may allow dead wood to accumulate,
allowing fires, when they occur, to be severe and affect most of the
patch; development and other human activities next to habitat patches
may allow more wildfires to be ignited; and the reduction in patch
size, through neighboring development, alteration of hydrology, or
encroachment by nonnative plants, makes it more likely that a larger
proportion of that patch will be affected during any given disturbance
event. Moreover, nearly all areas where riparian habitat could
potentially grow are modified by dams or water withdrawal and disrupted
by other activities, often in combination, that prevent the
reestablishment of riparian habitat. Patch size, when coupled with
habitat loss and Factor C and E threats, including proximity to
incompatible land uses which increases exposure to predators and
pesticides, is a significant cumulative threat to the western yellow-
billed cuckoo now and in the future.
Per section 4(b)(1)(A) of the Act, prior to making our
determination, we must first ``[take] into account those efforts, if
any, being made by any State or foreign nation, or any political
subdivision of a State or foreign nation, to protect such species,
whether by predator control, protection of habitat and food supply, or
other conservation practices, within any area under its jurisdiction,
or on the high seas.'' Restoration of riparian habitat on the Colorado,
Kern, and Sacramento Rivers and elsewhere will help reduce habitat
fragmentation, small patch size, and overall lack of habitat. Moreover,
at present, restoration is being done on a relatively small scale in
comparison to the need to reduce habitat fragmentation and increase the
overall extent of suitable habitat. DDT has been banned in the United
States for several decades, but use of DDT continues in Central and
South America, thus exposing western yellow-billed cuckoos during
migration and winter.
Through our analysis of the best available scientific and
commercial information on the abundance, life history, current
population status and trends, and the response of the species and its
habitat to natural and anthropogenic threats, we have determined that
the western yellow-billed cuckoo DPS meets the definition of threatened
under the Act, rather than endangered. The Act defines an endangered
species as any species that is ``in danger of extinction throughout all
or a significant portion of its range'' and a threatened species as any
species ``that is likely to become endangered
[[Page 61663]]
throughout all or a significant portion of its range within the
foreseeable future.'' Our general understanding of an ``endangered''
species is one that is currently on the brink of extinction in the
wild.
The geographic extent of the western yellow-billed cuckoo remains
rather widespread through much of its historic range, conferring some
measure of ecological and geographic redundancy and resilience.
Although there is a general decline in the overall population trend and
its breeding range has been reduced, the rate of the population decline
and contraction of its breeding range is not so severe to indicate
extinction is imminent for the western yellow-billed cuckoo. This
current downward trend is slow and not expected to increase in the near
future. The majority of large-scale habitat losses and conversions
through dam building and agricultural development have already
occurred, and we are not aware of any large-scale projects that would
affect the species to the extent that the current trend of decline
would change. Therefore, threats to the species and population declines
do not currently reach the level typical of an endangered species.
Because the western yellow-billed cuckoo does not face any known
sudden and calamitous threats, it is not a narrowly endemic species
vulnerable to extinction from elevated or cumulative threats, is not
yet restricted to a critically small range or critically low numbers,
and currently does not show any substantial reduction in numbers, it
would not meet the definition of ``endangered'' as determined by the
Act. More appropriately, we find that the western yellow-billed cuckoo
is likely to become endangered throughout all or a significant portion
of its range within the foreseeable future, based on the timing,
severity, and scope of the threats described above. Therefore, on the
basis of the best available scientific and commercial information, we
propose listing the western yellow-billed cuckoo DPS as threatened in
accordance with sections 3(6), 3(20), and 4(a)(1) of the Act.
Under the Act and our implementing regulations, a species may
warrant listing if it is threatened or endangered throughout all or a
significant portion of its range. The western yellow-billed cuckoo
proposed for listing in this rule is highly restricted to riparian
habitat, and the threats to the species and its habitat occur
throughout its breeding range. Therefore, we assessed the status of the
western yellow-billed cuckoo throughout its entire breeding range. The
threats to the survival of the species occur throughout the western
DPS' breeding range and are not restricted to any particular
significant portion of that range. We conclude that what affects the
entire breeding portion of the western DPS' range affects the status of
the entire western yellow-billed cuckoo throughout its breeding range,
including migration corridors and stopover areas. Accordingly, our
assessment and proposed determination applies to the western yellow-
billed cuckoo throughout its entire breeding range.
Available Conservation Measures
Conservation measures provided to species listed as endangered or
threatened under the Act include recognition, recovery actions,
requirements for Federal protection, and prohibitions against certain
practices. Recognition through listing results in public awareness and
conservation by Federal, State, tribal, and local agencies, private
organizations, and individuals. The Act encourages cooperation with the
States, and requires that recovery actions be carried out for all
listed species. The protection required by Federal agencies and the
prohibitions against certain activities are discussed, in part, below.
The primary purpose of the Act is the conservation of endangered
and threatened species and the ecosystems upon which they depend. The
ultimate goal of such conservation efforts is the recovery of these
listed species, so that they no longer need the protective measures of
the Act. Subsection 4(f) of the Act requires the Service to develop and
implement recovery plans for the conservation of endangered and
threatened species, unless the Secretary finds that such a plan will
not promote the conservation of the species. The recovery planning
process involves the identification of actions necessary to halt or
reverse the species' decline by addressing the threats to its survival
and recovery. The goal of this process is to restore listed species to
a point where they are secure, self-sustaining, and functioning
components of their ecosystems.
Recovery planning includes the development of a recovery outline
shortly after a species is listed, preparation of a draft and final
recovery plan, and revisions to the plan as significant new information
becomes available. The recovery outline indicates the species recovery
number, whether or not a recovery plan will be prepared and the
estimated date of completion, whether a recovery team will be
appointed, and what immediate actions are anticipated to conserve the
species. The recovery plan identifies site-specific management actions
that will achieve recovery of the species, measurable criteria that
determine when a species may be downlisted or delisted, and methods for
monitoring the recovery progress. Recovery plans also establish a
framework for agencies to coordinate their recovery efforts and provide
estimates of the cost of implementing recovery tasks. Recovery teams
(composed of species experts, Federal and State agencies,
nongovernmental organizations, and stakeholders) are often established
to develop recovery plans. When completed, the recovery outline, and
any draft recovery plan, or final recovery plan, subsequently
developed, will be available on our Web site (http://www.fws.gov/endangered) or from our Sacramento Fish and Wildlife Office (see FOR
FURTHER INFORMATION CONTACT).
Implementation of recovery actions generally requires the
participation of a broad range of partners, including other Federal
agencies, States, tribes, nongovernmental organizations, businesses,
and private landowners. Examples of recovery actions include habitat
restoration (for example, restoration of native vegetation), research,
captive propagation and reintroduction, and outreach and education. The
recovery of many listed species cannot be accomplished solely on
Federal lands because their range may occur primarily or solely on non-
Federal lands. To achieve recovery of these species requires
cooperative conservation efforts on private, State, and tribal lands.
If this species is listed, funding for recovery actions will be
available from a variety of sources, including Federal budgets, State
programs, and cost-share grants for non-Federal landowners, the
academic community, and nongovernmental organizations. In addition,
pursuant to section 6 of the Act, the States of California, Nevada,
Arizona, New Mexico, Texas, Colorado, Wyoming, Idaho, Washington, and
Oregon would be eligible for Federal funds to implement management
actions that promote the protection and recovery of the western yellow-
billed cuckoo. Information on our grant programs that are available to
aid species recovery can be found at: http://www.fws.gov/grants.
Although the western yellow-billed cuckoo is only proposed for
listing under the Act at this time, please let us know if you are
interested in participating in recovery efforts for this species.
Additionally, we invite you to submit any new information on this
species whenever it becomes available and any information you may have
for
[[Page 61664]]
recovery planning purposes (see FOR FURTHER INFORMATION CONTACT).
Section 7(a) of the Act requires Federal agencies to evaluate their
actions with respect to any species that is proposed or listed as
endangered or threatened and with respect to its critical habitat, if
any is designated. Regulations implementing this interagency
cooperation provision of the Act are codified at 50 CFR part 402.
Section 7(a)(4) of the Act requires Federal agencies to confer with the
Service on any action likely to jeopardize the continued existence of a
species proposed for listing or result in destruction or adverse
modification of proposed critical habitat. If a species is listed
subsequently, section 7(a)(2) of the Act requires Federal agencies to
ensure that activities they authorize, fund, or carry out are not
likely to jeopardize the continued existence of the species or destroy
or adversely modify its critical habitat. If a Federal action may
adversely affect a listed species or its critical habitat, the
responsible Federal agency must enter into formal consultation with the
Service.
Federal agency actions within or affecting the species' habitat
that may require conference or consultation or both as described in the
preceding paragraph include, but are not limited to, projects that will
result in removal or degradation of riparian vegetation, altered
streamflow or fluvial dynamics, or other habitat-altering activities on
Federal lands or as a result of issuance of section 404 CWA permits by
the USACE; construction and management of energy and power line rights-
of-way by the FERC; construction and maintenance of roads, highways, or
bridges by the Federal Highway Administration; grazing leases by the
USFS or the BLM; and projects funded through Federal loan programs.
Such projects may include, but are not limited to, construction or
modification of reservoirs, levees, bank stabilization structures,
water diversion and withdrawal projects, roads and bridges, utilities,
recreation sites, and other forms of development, and livestock
grazing.
The Act and its implementing regulations set forth a series of
general prohibitions and exceptions that apply to all endangered
wildlife. The prohibitions of section 9(a)(2) of the Act, codified at
50 CFR 17.21 for endangered wildlife, in part, make it illegal for any
person subject to the jurisdiction of the United States to take
(includes harass, harm, pursue, hunt, shoot, wound, kill, trap,
capture, or collect; or to attempt any of these), import, export, ship
in interstate commerce in the course of commercial activity, or sell or
offer for sale in interstate or foreign commerce any listed species.
Under the Lacey Act (18 U.S.C. 42-43; 16 U.S.C. 3371-3378), it is also
illegal to possess, sell, deliver, carry, transport, or ship any such
wildlife that has been taken illegally. Certain exceptions apply to
agents of the Service and State conservation agencies.
We may issue permits to carry out otherwise prohibited activities
involving endangered and threatened wildlife species under certain
circumstances. Regulations governing permits are codified at 50 CFR
17.22 for endangered species, and at 50 CFR 17.32 for threatened
species. With regard to endangered wildlife, a permit must be issued
for the following purposes: for scientific purposes, to enhance the
propagation or survival of the species, and for incidental take in
connection with otherwise lawful activities.
Our policy, as published in the Federal Register on July 1, 1994
(59 FR 34272), is to identify to the maximum extent practicable at the
time a species is listed, those activities that would or would not
constitute a violation of section 9 of the Act. The intent of this
policy is to increase public awareness of the effects of a proposed
listing on proposed and ongoing activities within the range of species
proposed for listing. The following activities could potentially result
in a violation of section 9 of the Act; this list is not comprehensive:
(1) Unauthorized collecting, handling, possessing, selling,
delivering, carrying, or transporting of western yellow-billed cuckoos
in the range of the western DPS, including import or export across
State lines and international boundaries, except for properly
documented antique specimens of these taxa at least 100 years old, as
defined by section 10(h)(1) of the Act.
(2) Intentional introduction of nonnative species that compete with
or prey upon western yellow-billed cuckoos in the range of the western
DPS, or degrade its habitat, including the intentional introduction of
nonnative vegetation, which may include, but is not limited to,
tamarisk, Russian olive, and giant reed.
(3) Unauthorized destruction or alteration of western yellow-billed
cuckoo habitat from alteration of the hydrology or fluvial geomorphic
processes that include, but are not limited to, channelization,
impoundment, bank stabilization, water extractions and diversions, and
channel clearing along any watercourse in which the western yellow-
billed cuckoo is known to occur.
(4) Unauthorized activities that result in removal, destruction, or
degradation of riparian vegetation from actions that include, but are
not limited to, streamside clearings, prescribed fire, off-road vehicle
use, human trampling, tree harvesting, and intensive livestock grazing
along any watercourse in which the western yellow-billed cuckoo is
known to occur.
(5) Unauthorized use of pesticides that would reduce insect prey
populations within or immediately adjacent to riparian areas in which
the western yellow-billed cuckoo is known to occur.
In California, if the western yellow-billed cuckoo is listed under
the Federal Endangered Species Act, the CESA (California Fish and Game
Code, Sec. 2050 et seq.) is automatically invoked, which would also
prohibit take of these species and encourage conservation by California
State government agencies. Further, the State may enter into agreements
with Federal agencies to administer and manage any area required for
the conservation, management, enhancement, or protection of endangered
species. Funds for these activities could be made available under
section 6 of the Act (Cooperation with the States). Thus, the Federal
protection afforded to this species by listing it as a threatened
species would be reinforced and supplemented by protection under State
law.
Questions regarding whether specific activities would constitute a
violation of section 9 of the Act should be directed to the Sacramento
Fish and Wildlife Office (see FOR FURTHER INFORMATION CONTACT).
Requests for copies of the regulations concerning listed animals and
general inquiries regarding prohibitions and permits may be addressed
to the U.S. Fish and Wildlife Service, Sacramento Fish and Wildlife
Office, Endangered Species Permits, 2800 Cottage Way, Room W-2605,
Sacramento, CA 95825 (telephone at 916-414-6600; facsimile at 916-414-
6712).
Peer Review
In accordance with our joint policy on peer review published in the
Federal Register on July 1, 1994 (59 FR 34270), we will seek the expert
opinions of at least three appropriate and independent specialists
regarding this proposed rule. The purpose of peer review is to ensure
that our critical habitat designation is based on scientifically sound
data, assumptions, and analyses. We have invited these peer reviewers
to comment
[[Page 61665]]
during the public comment period on our specific assumptions and
conclusions in this proposed rule.
We will consider all comments and information received during the
comment period on this proposed rule during our preparation of a final
determination. Accordingly, the final decision may differ from this
proposal.
Public Hearings
Section 4(b)(5) of the Act provides for one or more public hearings
on this proposal, if requested. Requests must be received within 45
days after the date of publication of this proposed rule in the Federal
Register. Such requests must be sent to the address shown in the FOR
FURTHER INFORMATION CONTACT. We will schedule public hearings on this
proposal, if any are requested, and announce the dates, times, and
places of those hearings, as well as how to obtain reasonable
accommodations, in the Federal Register and local newspapers at least
15 days before the hearing.
Required Determinations
Clarity of the Rule
Executive Order 12866 requires each agency to write regulations
that are easy to understand. We invite your comments on how to make
this rule easier to understand including answers to questions such as
the following: (1) Are the requirements in the rule clearly stated? (2)
Does the rule contain technical language or jargon that interferes with
its clarity? (3) Does the format of the rule (grouping and order of
sections, use of headings, paragraphing, etc.) aid or reduce its
clarity? (4) Would the rule be easier to understand if it were divided
into more (but shorter) sections? (5) Is the description of the rule in
the SUPPLEMENTARY INFORMATION section of the preamble helpful in
understanding the rule? What else could we do to make the proposed rule
easier to understand?
Send a copy of any comments that concern how we could make this
proposed rule easier to understand to Office of Regulatory Affairs,
Department of the Interior, Room 7229, 1849 C Street NW., Washington,
DC 20240. You also may email the comments to this address:
Exsec@ios.goi.gov.
Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.)
This rule does not contain any new collections of information that
require approval by OMB under the Paperwork Reduction Act of 1995 (44
U.S.C. 3501 et seq.). This rule will not impose recordkeeping or
reporting requirements on State or local governments, individuals,
businesses, or organizations. An agency may not conduct or sponsor, and
a person is not required to respond to, a collection of information
unless it displays a currently valid OMB control number.
National Environmental Policy Act (42 U.S.C. 4321 et seq.)
We have determined that environmental assessments and environmental
impact statements, as defined under the authority of the National
Environmental Policy Act of 1969 (42 U.S.C. 4321 et seq.), need not be
prepared in connection with regulations pursuant to section 4(a) of the
Act. We published a notice outlining our reasons for this determination
in the Federal Register on October 25, 1983 (48 FR 49244).
References Cited
A complete list of references cited in this rulemaking is available
on the Internet at http://www.regulations.gov and upon request from the
Sacramento Fish and Wildlife Office (see ADDRESSES for contact
information).
Authors
The primary authors of this document are the staff members of the
Sacramento Fish and Wildlife Office.
List of Subjects in 50 CFR Part 17
Endangered and threatened species, Exports, Imports, Reporting and
recordkeeping requirements, Transportation.
Proposed Regulation Promulgation
Accordingly, we propose to amend part 17, subchapter B of chapter
I, title 50 of the Code of Federal Regulations, as follows:
PART 17--[AMENDED]
0
1. The authority citation for part 17 continues to read as follows:
Authority: 16 U.S.C. 1361-1407; 1531-1544; 4201-4245; unless
otherwise noted.
0
2. Amend Sec. 17.11(h) by adding an entry for ``Cuckoo, yellow-billed
(Western DPS) to the List of Endangered and Threatened Wildlife in
alphabetical order under Birds, to read as follows:
Sec. 17.11 Endangered and threatened wildlife.
* * * * *
(h) * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------
Species Vertebrate
-------------------------------------------------------- population where Critical Special
Historic Range endangered or Status When listed habitat rules
Common name Scientific name threatened
--------------------------------------------------------------------------------------------------------------------------------------------------------
* * * * * * *
Birds
* * * * * * *
Cuckoo, yellow-billed (Western Coccyzus americanus. U.S.A., Canada, U.S.A. (AZ, CA, CO T NA NA
DPS). Mexico. (western), ID, MT
(western), NM
(western), NV, OR,
TX (western), UT,
WA, WY (western)),
Canada (British
Columbia), Mexico
(Baja California,
Baja California
Sur, Chihuahua,
Durango (western),
Sinaloa, Sonora)).
[[Page 61666]]
* * * * * * *
* * * * * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------
* * * * *
Dated: September 19, 2013.
Dan Ashe,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 2013-23725 Filed 10-2-13; 8:45 am]
BILLING CODE 4310-55-P