[Federal Register Volume 83, Number 71 (Thursday, April 12, 2018)]
[Proposed Rules]
[Pages 15758-15780]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-06864]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR 17
[Docket No. FWS-R3-ES-2018-0005; FXES11130900000]
RIN 1018-BC01
Endangered and Threatened Wildlife and Plants; Removing the
Kirtland's Warbler From the Federal List of Endangered and Threatened
Wildlife
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Proposed rule.
-----------------------------------------------------------------------
SUMMARY: Under the authority of the Endangered Species Act of 1973, as
amended (Act), we, the U.S. Fish and Wildlife Service (Service),
propose to remove the Kirtland's warbler (Setophaga kirtlandii) from
the Federal List of Endangered and Threatened Wildlife (List) due to
recovery. This determination is based on a thorough review of the best
available scientific and commercial information, which indicates that
the threats to the species have been eliminated or reduced to the point
that the species has recovered and no longer meets the definition of
endangered or threatened under the Act.
DATES: We will accept comments received or postmarked on or before July
11, 2018. We must receive requests for public hearings, in writing, at
the address shown in FOR FURTHER INFORMATION CONTACT by May 29, 2018.
ADDRESSES: Written comments: 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-R3-ES-2018-0005,
which is the docket number for this rulemaking. Then, click on the
Search button. On the resulting page, in the Search panel on the left
side of the screen, under the Document Type heading, click on the
Proposed Rules link to locate this document. 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: FWS-R3-ES-2018-0005, U.S. Fish and Wildlife
Service, MS: BPHC; 5275 Leesburg Pike, Falls Church, VA 22041-3803.
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 Information Requested, below, for more information).
Document availability: This proposed rule and supporting documents
are available on http://www.regulations.gov. In addition, the
supporting file for this proposed rule will be available for public
inspection, by appointment, during normal business hours, at the
Michigan Ecological Services Field Office, 2651 Coolidge Road, Suite
101, East Lansing, MI 48823; telephone 517-351-2555.
FOR FURTHER INFORMATION CONTACT: Scott Hicks, Field Supervisor,
Michigan Ecological Services Field Office, 2651 Coolidge Road, Suite
101, East Lansing, MI 48823; telephone 517-351-2555; facsimile 517-351-
1443. If you use a telecommunications device for the deaf (TDD), please
call the Federal Relay Service at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Executive Summary
Purpose of Regulatory Action
This action proposes to remove the Kirtland's warbler from the
Federal List of Endangered and Threatened Wildlife in title 50 of the
Code of Federal Regulations (50 CFR 17.11(h)) based on the species'
recovery. Removing a species from the List (``delisting'') can only be
completed by issuing a rule.
Basis for Action
We may delist a species if the best scientific and commercial data
indicate the species is neither an endangered species nor a threatened
species for one or more of the following reasons: (1) The species is
extinct; (2) the species has recovered; or (3) the original data used
at the time the species was classified were in error (50 CFR 424.11).
Here, we have determined that the species may be delisted based on
recovery. A species may be delisted based on recovery only if the best
scientific and commercial data indicate that it is no longer endangered
or threatened.
The threats that led to the species being listed under the Act
(primarily loss of the species' habitat and effects of brood parasitism
by brown-headed cowbirds) have been removed, ameliorated, or are being
appropriately managed by the actions of multiple conservation partners
over the past 50 years.
Information Requested
Public Comments
Any final action resulting from this proposed rule will be based on
the best scientific and commercial data available and be as accurate as
possible. Therefore, we request comments or information from other
concerned governmental agencies, Native American Tribes, the scientific
community, industry, or other interested parties concerning this
proposed rule. The comments that will be most useful and likely to
influence our decisions are those supported by data or peer-reviewed
studies and those that include citations to, and analyses of,
applicable laws and regulations. Please make your comments as specific
as possible and explain the basis for them. In addition, please include
sufficient information with your comments to allow us to authenticate
any scientific or commercial data you reference or provide. In
particular, we seek comments concerning the following:
(1) Reasons we should or should not delist the Kirtland's warbler.
(2) New information on the historical and current status, range,
distribution, and population size of the Kirtland's warbler.
(3) New information on the known and potential threats to the
Kirtland's warbler on its breeding grounds, on its wintering grounds,
and during migration, including brood parasitism, and habitat
availability.
(4) Information on the timing and extent of the effects of climate
change on the Kirtland's warbler.
(5) New information regarding the life history, ecology, and
habitat use of the Kirtland's warbler.
(6) Current or planned activities within the geographic range of
the Kirtland's warbler that may impact or benefit the species.
(7) The adequacy of conservation agreements that would be
implemented if the species is delisted.
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 (16 U.S.C.
1531 et seq.) directs that determinations as to whether any species is
an endangered or threatened species must be made ``solely on the basis
of the best scientific and commercial data available.''
Prior to issuing a final rule on this proposed action, we will take
into consideration all comments and any additional information we
receive. Such
[[Page 15759]]
information may lead to a final rule that differs from this proposal.
All comments and recommendations, including names and addresses, will
become part of the administrative record.
You may submit your comments and materials concerning the proposed
rule by one of the methods listed in ADDRESSES. Comments must be
submitted to http://www.regulations.gov before 11:59 p.m. (Eastern
Time) on the date specified in DATES. We will not consider hand-
delivered comments that we do not receive, or mailed comments that are
not postmarked, by the date specified in DATES.
We will post your entire comment--including your personal
identifying information--on http://www.regulations.gov. If you provide
personal identifying information in your comment, 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.
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, Michigan Ecological Services Field Office (see FOR FURTHER
INFORMATION CONTACT).
Public Hearing
Section 4(b)(5)(E) of the Act provides for one or more public
hearings on this proposed rule, if requested. We must receive requests
for public hearings, in writing, at the address shown in FOR FURTHER
INFORMATION CONTACT by the date shown in DATES. We will schedule public
hearings on this proposal if any are requested, and announce the
details of those hearings, as well as how to obtain reasonable
accommodations, in the Federal Register at least 15 days before the
first hearing.
Peer Review
In accordance with our 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 determination is based on scientifically sound data,
assumptions, and analyses. We will send peer reviewers copies of this
proposed rule immediately following publication in the Federal
Register. We will invite these peer reviewers to comment during the
public comment period. We will consider all comments and information we
receive from peer reviewers during the comment period on this proposed
rule, as we prepare a final rule.
Previous Federal Actions
The Kirtland's warbler was listed as endangered under the
Endangered Species Preservation Act on March 11, 1967 (32 FR 4001),
primarily due to threats associated with limited breeding habitat and
brown-headed cowbird (Molothrus ater) brood parasitism. The species is
currently listed as endangered under the Endangered Species Act of
1973, as amended (16 U.S.C. 1531 et seq.). We developed a recovery plan
in 1976 (USFWS 1976) and revised the plan on September 30, 1985 (USFWS
1985).
On June 29, 2012, we published a document in the Federal Register
(77 FR 38762) announcing that we were conducting a 5-year review of the
status of Kirtland's warbler under section 4(c)(2) of the Act. In that
document, we requested that the public provide us any new information
concerning this species. The 5-year status review, completed in August
2012 (USFWS 2012), resulted in a recommendation to change the status of
this species from endangered to threatened. The 2012 5-year status
review is available on the Service's website at https://www.fws.gov/midwest/endangered/birds/Kirtland/index.html, and via the Service's
Environmental Conservation Online System (ECOS) (https://ecos.fws.gov/ecp0/profile/speciesProfile?spcode=B03I).
On November 14, 2013, we published a rule in the Federal Register
(78 FR 68370) revising the taxonomy to reflect the scientifically
accepted taxonomy and nomenclature of this species (Setophaga
kirtlandii (= D. kirtlandii)).
On April 17, 2017, we published a document in the Federal Register
(82 FR 18156) announcing initiation of 5-year status reviews for eight
endangered animal species, including Kirtland's warbler, and requested
information on the species' status. This proposed rule constitutes
completion of that 5-year status review.
Species Information
Taxonomy
The Kirtland's warbler is a songbird classified in the Order
Passeriformes, Family Parulidae. Spencer Baird originally described
this species in 1852, and named it Sylvicola kirtlandii after Dr. Jared
P. Kirtland of Cleveland, Ohio (Baird 1872, p. 207). The American
Ornithologists' Union Committee on Classification and Nomenclature--
North and Middle America recently changed the classification of the
Parulidae, which resulted in three genera (Parula, Dendroica, and
Wilsonia) being deleted and transferred to the genus Setophaga (Chesser
et al. 2011, p. 606). This revision was adopted by the Service on
February 12, 2014 (see 78 FR 68370; November 14, 2013).
Distribution
The Kirtland's warbler is a neotropical migrant that breeds in jack
pine (Pinus banksiana) forests in northern Michigan, Wisconsin, and
Ontario. This species has one of the most geographically restricted
breeding distributions of any mainland bird in the continental United
States. Breeding habitat within the jack pine forest is both highly
specific and disturbance-dependent, and likely was always limited in
extent (Mayfield 1960, pp. 9-10; Mayfield 1975, p. 39). Similarly, the
known wintering range is primarily restricted to The Bahamas (Cooper et
al. 2017, p. 213).
Kirtland's warblers are not evenly distributed across their
breeding range. More than 98 percent of all singing males have been
counted in the northern Lower Peninsula of Michigan since population
monitoring began in 1951 (Michigan Department of Natural Resources
(MDNR), Service (USFWS), U.S. Forest Service (USFS), unpubl. data). The
core of the Kirtland's warbler's breeding range is concentrated in five
counties in northern lower Michigan (Ogemaw, Crawford, Oscoda, Alcona,
and Iosco), where nearly 85 percent of the singing males were recorded
between 2000 and 2015, with over 30 percent counted in Ogemaw County
alone and over 21 percent in just one township during that same time
period (MDNR, USFWS, USFS, unpubl. data).
Kirtland's warblers have also been observed in Ontario periodically
since 1900 (Samuel 1900, pp. 391-392), and in Wisconsin since the 1940s
(Hoffman 1989, p. 29). Systematic searches for the presence of
Kirtland's warblers in States and provinces adjacent to Michigan,
however, did not begin until 1977 (Aird 1989, p. 32; Hoffman 1989, p.
1). Shortly after these searches began, male Kirtland's warblers were
found during the breeding season in Ontario (in 1977), Quebec (in
1978), Wisconsin (in 1978), and the Upper Peninsula of Michigan (in
1982) (reviewed in Aird 1989, pp. 32-35). Nesting was confirmed in the
Upper Peninsula in 1996 (Weinrich 1996, p. 2; Weise and Weinrich 1997,
p. 2), and in Wisconsin and Ontario in 2007 (Richard 2008, pp. 8-10;
Trick et al. 2008, pp. 97-98).
[[Page 15760]]
Systematic searches to confirm nesting in states and provinces adjacent
to Michigan have not been consistent across years. Female Kirtland's
warblers are often observed with singing males, however, and nesting is
generally assumed to occur at most sites where singing males are
present (Probst et al. 2003, p. 369; MDNR, USFWS, USFS, unpubl. data).
Singing males have been observed in the Upper Peninsula since 1993,
with the majority of observations in the central and eastern Upper
Peninsula (MDNR, USFWS, USFS, unpubl. data). In Wisconsin, nesting has
been confirmed in Adams County every year since 2007, and has recently
expanded into Marinette and Bayfield Counties (USFWS 2017, pp. 2-4).
Scattered observations of mostly solitary birds have also occurred in
recent years at several other sites in Douglas, Vilas, Washburn, and
Jackson Counties in Wisconsin. Similarly, in Ontario, nesting was
confirmed in Renfrew County from 2007 to 2016 (Richard 2013, p. 152;
Tuininga 2017, pers. comm.), and reports of Kirtland's warblers present
during the breeding season have occurred in recent years in both
northern and southern Ontario (Tuininga 2017, pers. comm.).
The current distribution of breeding Kirtland's warblers
encompasses the known historical breeding range of the species based on
records of singing males observed in Michigan's northern Lower
Peninsula, Wisconsin, and Ontario (Walkinshaw 1983, p. 23). In 2015,
the number of singing males confirmed during the formal census period
in Wisconsin (19), Ontario (20), and the Upper Peninsula (37)
represented approximately 3 percent of the total singing male
population (Environment Canada, MDNR, USFWS, USFS, Wisconsin DNR
(WNDR), unpubl. data), demonstrating the species' reliance on their
core breeding range in Michigan's northern Lower Peninsula. The number
of Kirtland's warblers that could ultimately exist outside of the core
breeding range is unknown; however, these peripheral individuals do
contribute to a wider distribution.
Given the geographical extent of the warbler's historical range,
peripheral Kirtland's warblers and habitat (outside the northern Lower
Peninsula of Michigan) may help maintain the breadth of environmental
diversity within the species, and increase the species' adaptive
diversity (ability to adapt to changing environmental conditions over
time) (Shaffer and Stein 2000, pp. 308-311). In Michigan's northern
Lower Peninsula, the Kirtland's warbler's breeding habitat is spread
over an approximately 15,540 square kilometer (km) (6,000 square mile)
non-contiguous area. Therefore, within Michigan's northern Lower
Peninsula, the Kirtland's warbler's breeding habitat is unlikely to
uniformly experience catastrophic events (e.g., wildfire) over that
large an area. Although the number of Kirtland's warblers in Michigan's
Upper Peninsula, Wisconsin, and Ontario currently represent a small
percentage of the total population, Kirtland's warblers are
successfully reproducing in these areas. The Kirtland's warbler's
expansion into Michigan's Upper Peninsula, Wisconsin, and Ontario
(Canada), therefore, could represent a future potential for the
establishment of additional breeding territories outside of northern
lower Michigan and would further increase the ability of the species to
withstand catastrophic events by reducing the risk of such an event
effecting the entire population over an even larger spatial scale.
Kirtland's warblers are more difficult to detect during the winter
and are infrequently observed. The warblers appear to be unevenly
distributed across the landscape; they tend to hide in low-lying, dense
vegetation; and males do not generally sing during the winter (Currie
et al. 2003, pp. 1-2; Currie et al. 2005a, p. 97). Extensive searches
in the past produced few sightings of wintering Kirtland's warblers
(Mayfield 1996, pp. 36-38; Lee et al. 1997, p. 21). A long-standing
body of evidence dating to 1841, when the very first specimen was
collected off the coast of Abaco Island (Stone 1986, p. 2), indicates
that Kirtland's warblers winter largely within The Bahamas. The Bahamas
is an archipelago of approximately 700 low-lying islands stretching
more than 1,046 km (650 miles) from near the eastern coast of Florida
to the southeastern tip of Cuba. Eleuthera and Cat Islands support the
largest known population of wintering Kirtland's warblers (Sykes and
Clench 1998, pp. 249-250; Cooper unpubl. data), although other islands
have not been studied as intensively and potentially support
substantial numbers. Within The Bahamas, Kirtland's warblers have been
observed on several islands including The Abacos, Andros, Cat Island,
Crooked Island, Eleuthera, The Exumas, Grand Bahama Island, Long
Island, and San Salvador (Blanchard 1965, pp. 41-42; Hundley 1967, pp.
425-426; Mayfield 1972, pp. 347-348; Mayfield 1996, pp. 37-38; Haney et
al. 1998, p. 202; Sykes and Clench 1998; Cooper unpubl. data). Haney et
al. (1998, p. 205) found that only 3 of 107 reports originated from
outside of The Bahamas: Two sightings from northern Dominican Republic,
and one sighting from coastal Mexico. In addition, recent winter
reports of solitary individuals have originated from Bermuda (Amos
2005, p. 3) and Cuba (Isada 2006, p. 462; Sorenson and Wunderle 2017).
Cooper et al. (2017, p. 209) used geolocators to track Kirtland's
warblers to determine distribution for 27 birds on the wintering
grounds. The estimated wintering ranges of 18 tracked males overlapped
primarily the central Bahamas (Eleuthera, Cat Island, The Exumas, Long
Island, Rum Cay, San Salvador), 4 males overlapped primarily the
western Bahamas (Grand Bahama, The Abacos, Nassau, Andros Island), and
4 males overlapped primarily the eastern Bahamas (Acklins Islands,
Mayaguana, Great Inagua) or Turks and Caicos. One male appeared to
winter in central Cuba (Cooper et al. 2017, p. 211).
Although the known wintering range appears restricted primarily to
The Bahamas, many of the islands in the Caribbean basin are uninhabited
by people or have had limited avian survey efforts, which may constrain
our ability to comprehensively describe the species' wintering
distribution. Kirtland's warblers readily shift sites on the wintering
grounds based on habitat availability and food resources, and colonize
new areas following disturbance (Wunderle et al. 2007, p. 123; Wunderle
et al. 2010, p. 134; Wunderle et al. 2014, p. 44). Suitable habitat
exists on other islands, both within The Bahamas and elsewhere in the
Caribbean basin, potentially providing habitat and buffering against
the effects of catastrophic events such as hurricanes.
Breeding Habitat
The Kirtland's warbler's breeding habitat consists of jack pine-
dominated forests with sandy soil and dense ground cover (Walkinshaw
1983, p. 36), most commonly found in northern lower Michigan, with
scattered locations in the Upper Peninsula of Michigan, Wisconsin, and
Ontario. Jack pine-dominated forests of the northern Great Lakes region
historically experienced large, frequent, and catastrophic stand-
replacing fires (Cleland et al. 2004, p. 313). These fires occurred
approximately every 60 years, burned approximately 85,420 hectares (ha)
(211,077 acres (ac)) per year, and resulted in jack pine comprising 53
percent of the total land cover (Cleland et al. 2004, pp. 315-317).
Modern wildfire suppression has since increased the average fire return
interval within this same landscape to approximately
[[Page 15761]]
775 years, decreased the amount of area burned to approximately 6,296
ha (15,558 ac) per year, and reduced the contribution of jack pine to
37 percent of the current land cover (Cleland et al. 2004, p. 316). The
overall effect has been a reduction in the extent of dense jack pine
forest, and in turn, the Kirtland's warbler's breeding habitat.
Kirtland's warblers generally occupy jack pine stands that are 5 to
23 years old and at least 12 ha (30 ac) in size (Donner et al. 2008, p.
470). The most obvious difference between occupied and unoccupied
stands is the percent canopy cover (Probst 1988, p. 28). Stands with
less than 20 percent canopy cover are rarely used for nesting (Probst
1988, p. 28). Tree canopy cover reflects overall stand structure,
combining individual structural components such as tree stocking,
spacing, and height factors (Probst 1988, p. 28). Tree canopy cover,
therefore, may be an important environmental cue for Kirtland's
warblers when selecting nesting areas.
Occupied stands usually occur on dry, excessively drained,
nutrient-poor glacial outwash sands (Kashian et al. 2003, pp. 151-153).
Stands are structurally homogeneous with trees ranging 1.7 to 5.0
meters (m) (5.5 to 16.4 feet (ft)) in height, and are generally of
three types: Wildfire-regenerated, planted, and unburned-unplanted
(Probst and Weinrich 1993, p. 258). Wildfire-regenerated stands occur
naturally following a stand-replacing fire from serotinous seeding
(seed cones remain closed on the tree with seed dissemination in
response to an environmental trigger, such as fire). Planted stands are
stocked with jack pine saplings after a clear cut. Unburned-unplanted
stands originate from clearcuts that regenerate from non-serotinous,
natural seeding, and thus do not require fire to release seeds.
Optimal habitat is characterized as large stands (more than 32 ha
(80 ac)) composed of 8 to 20-year-old jack pines that regenerated after
wildfires, with 27 to 60 percent canopy cover, and more than 5,000
stems per hectare (2,023 stems per acre) (Probst and Weinrich 1993, pp.
262-263). The poor quality and well-drained soils reduce the risk of
nest flooding and maintain low shrubs that provide important cover for
nesting and brood-rearing. Yet as jack pine saplings grow in height,
percent canopy cover increases, causing self-pruning of the lower
branches and changes in light regime, which diminishes cover of small
herbaceous understory plants (Probst 1988, p. 29; Probst and Weinrich
1993, p. 263; Probst and Donnerwright 2003, p. 331). Bocetti (1994, p.
122) found that nest sites were selected based on higher jack pine
densities, higher percent cover of blueberry, and lower percent cover
of woody debris than would be expected if nests were placed at random.
Due to edge effects associated with low area-to-perimeter ratios,
predation rates may be higher for Kirtland's warblers nesting in small
patches bordered by mature trees than in large patches (Probst 1988, p.
32; Robinson et al. 1995, pp. 1988-1989; Helzer and Jelinski 1999, p.
1449). Foraging requirements may also be negatively influenced as jack
pines mature (Fussman 1997, pp. 7-8).
Conversely, marginal habitat is characterized as jack pine stands
with at least 20 to 25 percent tree canopy cover and a minimum density
of 2,000 stems per hectare (809 stems per acre, Probst and Weinrich
1993, pp. 261-265; Nelson and Buech 1996, pp. 93-95), and is often
associated with unburned-unplanted areas (Donner et al. 2010, p. 2).
Probst and Hayes (1987, p. 237) indicate that the main disadvantage of
marginal habitat is reduced pairing success. Evidence from Wisconsin
and Canada, however, has shown an ability of Kirtland's warblers to
successfully reproduce in areas with smaller percentages of jack pine
and with significant components of red pine (Pinus resinosa) and pin
oak (Quercus palustris) (Mayfield 1953, pp. 19-20; Orr 1975, pp. 59-60;
USFWS 1985, p. 7; Fussman 1997, p. 5; Anich et al. 2011, p. 201;
Richard 2013, p. 155; Richard 2014, p. 307). Use of these areas in
Michigan is rare and occurs for only short durations (Huber et al.
2001, p. 10). In Wisconsin, however, breeding has occurred primarily in
red pine plantations that have experienced extensive red pine mortality
and substantial natural jack pine regeneration (Anich et al. 2011, p.
204). Preliminary investigation (Anich et al. 2011, p. 204) suggests
that in this case, a matrix of openings and thickets has produced
conditions suitable for Kirtland's warblers, and that the red pine
component may actually prolong the use of these sites due to a longer
persistence of low live branches on red pines. Habitat conditions in
documented Kirtland's warbler breeding areas in Ontario had similar
ground cover to breeding sites in Michigan and Wisconsin, although tree
species composition was more similar to Wisconsin sites than Michigan
sites (Richard 2014, p. 306). The tree species composition at the
Canadian sites also had high levels of red pine (up to 71 percent),
similar to the plantations in Wisconsin (Anich et al. 2011, p. 201;
Richard 2014, p. 307).
Habitat management to benefit Kirtland's warblers began as early as
1957 on State forest land and 1962 on Federal forest land (Mayfield
1963, pp. 217-219; Radtke and Byelich 1963, p. 209). Efforts increased
in 1981, with the establishment of an expanded habitat management
program to supplement wildfire-regenerated habitat and ensure the
availability of relatively large patches of early successional jack
pine forest for nesting (Kepler et al. 1996, p. 16). In the 1981
Management Plan for Kirtland's Warbler Habitat (USFS and MDNR 1981, p.
23), approximately 29,987 ha (74,100 ac) of Michigan State forest lands
and about 21,650 ha (53,500 ac) of Federal forest lands were identified
as lands suitable and manageable for Kirtland's warbler breeding
habitat. That plan also provided prescriptions and guidelines to be
used in protecting and improving identified nesting habitat. Contiguous
stands or stands in close proximity were grouped into 23 areas referred
to as Kirtland's Warbler Management Areas (KWMAs). KWMAs are
administrative boundaries that describe parcels of land dedicated to
and managed for Kirtland's warbler breeding habitat. The KWMAs were
further subdivided into cutting blocks containing 200 or more acres of
contiguous stands. These acreages were determined by factoring an
average population density of one breeding pair per 12 ha (30 ac) into
a 45 to 50 year commercial harvest rotation, which would produce
suitable habitat as well as marketable timber (USFWS 1985, p. 21). At
the time the recovery plan was updated, there were 51,638 ha (127,600
ac) of public forest lands designated for Kirtland's warbler habitat
management in order to meet Kirtland's warbler recovery program
objectives (USFWS 1985, p. 18). Data collected from the annual singing
male census from 1980 to 1995 indicated that a breeding pair used
closer to 15 ha (38 ac) within suitably aged habitat (Bocetti et al.
2001, p. 1). Based on these data, the Kirtland's Warbler Recovery Team
recommended increasing the total amount of managed habitat to 76,890 ha
(190,000 ac) (Ennis 2002, p. 2).
Wintering Habitat
On the wintering grounds, Kirtland's warblers occur in early
successional scrublands, characterized by dense, low, broadleaf shrubs
of varied foliage layers with small openings, resulting from natural or
anthropogenic disturbances (locally known as low coppice) (Maynard
1896, pp. 594-595; Challinor 1962, p. 290; Mayfield 1972, p. 267;
Mayfield 1992, p. 3; Mayfield 1996, pp. 38-39; Radabaugh 1974, p. 380;
Lee et al. 1997, p. 23; Haney et al. 1998, p. 207; Sykes and Clench
1998, p. 256;
[[Page 15762]]
Wunderle et al. 2007, p. 123; Wunderle et al. 2010, p. 133).
Clearing vegetation by bulldozers, wildfires, hurricanes, and local
agricultural practices, such as ``slash and burn,'' can create suitable
habitat on Eleuthera Island (Wunderle et al. 2007, p. 124), and the
Kirtland's warbler likely benefited from local declines in agriculture
as fallow lands reverted to early successional scrublands (Sykes and
Clench 1998, p. 247). Kirtland's warblers typically occupy wintering
sites 3 to 28 years (mean is approximately 14 years) after human
disturbance (Wunderle et al. 2010, p. 127). As local food resources
diminish in abundance, these sites may not be sufficient to sustain an
individual for an entire winter; therefore, individuals must move
widely from patch to patch, tracking changes in fruit abundance
(Wunderle et al. 2007, p. 123; Wunderle et al. 2010, p. 134; Wunderle
et al. 2014, p. 44).
Migration and Stopover Habitat
Spring departure from the wintering grounds is estimated to occur
from late-April to early May, and arrival on the breeding grounds
approximately 15 days later based on data from geolocators attached to
27 male Kirtland's warblers in 2012 and 2014 (Cooper et al. 2017, p.
212). These dates are similar to direct observations of color-banded
birds arriving on the breeding grounds (Rockwell et al. 2012, p. 746)
and when comparing the latest observation of birds present on the
wintering grounds with the date first resighted on their breeding
grounds (Ewert et al. 2012, p. 11). Male Kirtland's warblers have been
observed arriving on the breeding grounds between May 1 and June 5
(Petrucha 2011, p. 17; Rockwell et al. 2012, p. 747), with a mean range
between May 14 and May 15, and with the first females arriving a week
or so after the first males (Mayfield 1960, pp. 41-42; Rockwell 2013,
pp. 48-49).
Cooper et al. (2017, p. 212) determined that fall migration of
adult males began with departure dates in late September through late
October and arrival on the wintering grounds in mid-October to early
November. The earliest recorded sighting in The Bahamas was August 20
(Robertson 1971, p. 48). Data from recovered geolocators showed that
most Kirtland's warblers exhibited a loop migration, with fall
migration occurring farther east than spring migration (Cooper et al.
2017, p. 214). Nearly all males departed the breeding grounds and flew
in an easterly direction, spending time in southeastern Ontario or in
the eastern Great Lakes region of the United States (Cooper et al.
2017, pp. 211, 213). Fall migration proceeded in a general southern
direction, departing the mainland United States along the Carolina
coastline (Cooper et al. 2017, pp. 211, 213). Spring migration followed
a more westerly path, with landfall occurring in Florida and Georgia
(Cooper et al. 2017, pp. 213, 216). An additional stopover site was
identified in the western Lake Erie basin (Cooper et al. 2017, p. 216).
Petrucha et al. (2013, p. 383) analyzed 562 records of Kirtland's
warblers observed during migration and found that migration records
were spread over most of the United States east of the Mississippi
River, clustered around the Great Lakes and Atlantic Ocean coastlines.
Migrating Kirtland's warblers have been observed in a variety of
habitats, including shrub/scrub, residential, park, orchard, woodland,
and open habitats (Petrucha et al. 2013, p. 390). There is some
evidence that dense vegetation less than 1.5 m (4.9 ft) in height may
be important to migrating Kirtland's warblers (Stevenson and Anderson
1994, p. 566). The majority of migration records (82 percent) described
the habitat as shrub/scrub, similar in structure to that on the
breeding and wintering grounds (Petrucha et al. 2013, p. 384).
Biology
Diet and Foraging
On the breeding grounds, Kirtland's warblers are primarily
insectivorous and forage by gleaning (plucking insects from) pine
needles, leaves, and ground cover, occasionally making short sallies,
hover-gleaning at terminal needle clusters, and gathering flying
insects on the wing. Kirtland's warblers have been observed foraging on
a wide variety of prey items, including various types of larvae, moths,
flies, beetles, grasshoppers, ants, aphids, spittlebugs, and
blueberries (Mayfield 1960, pp. 18-19; Fussman 1997, p. 33). Deloria-
Sheffield et al. (2001, p. 385) identified similar taxa from fecal
samples collected from Kirtland's warblers, but also observed that from
July to September, homopterans (primarily spittlebugs), hymenopterans
(primarily ants) and blueberries were proportionally greater in number
than other taxa among samples. Deloria-Sheffield et al. (2001, p. 386)
suggested that differences in the relative importance of food items
between spring foraging observations and late summer fecal samples were
temporal and reflected a varied diet that shifts as food items become
more or less available during the breeding season. Within nesting
areas, arthropod numbers peak at the same time that most first broods
reach the fledging stage (Fussman 1997, p. 27). Planted and wildfire-
regenerated habitats were extremely similar in terms of arthropod
diversity, abundance, and distribution, suggesting that current habitat
management techniques are effective in simulating the effects that
wildfire has on food resources for Kirtland's warblers (Fussman 1997,
p. 63).
On the wintering grounds, Kirtland's warblers rely on a mixed diet
of fruit and arthropods. During foraging observations, 69 percent of
Kirtland's warblers consumed fruits, such as snowberry (Chiococca
alba), wild sage (Lantana involucrata), and black torch (Erithalis
fruticosa), with wild sage being the overwhelmingly predominant food
choice (Wunderle et al. 2010, pp. 129-130). Despite variation in food
availability among sites and winters, the proportion of fruit and
arthropods in fecal sample of Kirtland's warblers was consistent
(Wunderle et al. 2014, p. 25). Food abundance was a reliable predictor
of site fidelity, with birds shifting location to sites with higher
biomass of ripe fruit and ground arthropods during the late winter
(Wunderle et al. 2014, p. 31).
Demographics
The average life expectancy of adult Kirtland's warblers is
approximately 2.5 years (Walkinshaw 1983, pp. 142-143). The oldest
Kirtland's warbler on record was an 11-year old male, which, when
recaptured in the Damon KWMA in 2005, appeared to be in good health and
paired with a female (USFS, unpubl. data).
Overall, Kirtland's warbler annual survival estimates are similar
to those of other wood warblers (reviewed in Faaborg et al. 2010, p.
12). Reported survival rates of the Kirtland's warbler varied by sex
and age classes (Mayfield 1960, pp. 204-207; Walkinshaw 1983, pp. 123-
143; Bocetti et al. 2002, p. 99; Rockwell et al. 2017, p. 723; Trick,
unpubl. data). Rockwell et al. (2017, pp. 719-721) analyzed mark-
recapture data from 2006-2010 on breeding grounds in Michigan and from
2003-2010 on the wintering grounds in The Bahamas, and determined the
mean annual survival estimates for adults and yearlings were 0.58 and
0.55, respectively. Rockwell et al. (2017, p. 722), also found that
monthly survival probabilities were relatively high when birds were
stationary on the wintering and breeding grounds, and were
substantially lower during the migratory period, which has the highest
mortality
[[Page 15763]]
rate out of any phase of the annual cycle, accounting for 44 percent of
annual mortality. Survival probability was positively correlated to
March rainfall in the previous year, suggesting the effects of rain on
the wintering grounds carried over to affect annual survival in
subsequent seasons. Reduced rain can result in lower available food
resources for Kirtland's warblers, which could result in poorer body
condition; has been shown to make them less likely to survive the
subsequent spring migration (Rockwell et al. 2017, pp. 721-722); and
lowers reproductive success during the breeding season (Rockwell et al.
2012, p. 745).
Genetics
From the information available, it appears that Kirtland's warblers
display winter and breeding-ground panmixia (mixing of individuals
across locations within the population). In 2007, eight birds examined
from six different wintering sites on Eleuthera Island were found on
breeding territories in the Damon KWMA in Ogemaw County, Michigan
(Ewert, unpubl. data). Additionally, four other birds banded from one
wintering site on Eleuthera Island were found on breeding territories
across four counties in northern lower Michigan. Kirtland's warblers
are also known to regularly move between KWMAs in northern lower
Michigan during the breeding season (Probst et al. 2003, p. 371). This
suggests that the warbler's population exhibits panmictic (a group of
interbreeding individuals where all individuals in the population are
potential reproductive partners) rather than metapopulation (groups of
interbreeding individuals that are geographically distinct) demographic
characteristics (Esler 2000, p. 368).
King et al. (2005, p. 569) analyzed blood samples from 14 wintering
Kirtland's warblers on Eleuthera Island, isolated and characterized 23
microsatellite DNA markers specific to the species, and found moderate
to high levels of allelic diversity and heterozygosity that demonstrate
the potential variability of the individual loci that were developed.
Wilson et al. (2012, pp. 7-9) used 17 microsatellite loci (12 were
developed by King et al. 2015, p. 570) to measure and compare the
genetic diversity from breeding Kirtland's warblers in Oscoda County,
MI. Wilson et al. (2012, pp. 7-9) tested for genetic bottlenecks,
temporal changes in genetic diversity, and effective population size
using samples from 3 time periods (1903-1912, 1929-1955, and 2008-
2009). Their results showed no evidence of a bottleneck in the oldest
(1903-1912) sample, indicating that any population declines prior to
that point may have been gradual. Although population declines have
been observed since then, there was only weak genetic evidence of a
bottleneck in the two more recent samples (no bottleneck detected in
two of three possible models for each sample). The study showed a
slight loss of allelic richness between the oldest and more recent
samples (estimated to be 1.7 alleles per locus), but no significant
difference in heterozygosity between samples and no evidence of
inbreeding. Effective population size estimates varied depending on the
methods used, but none were low enough to indicate that inbreeding or
rapid loss of genetic diversity were likely in the future. Based on the
available data, genetic diversity does not appear to be a limiting
factor for the Kirtland's warbler, or indicate the need for genetic
management at this time.
Abundance and Population Trends
Prior to 1951, the size of the Kirtland's warbler population was
extrapolated from anecdotal observations and knowledge about breeding
and wintering habitat conditions. The Kirtland's warbler population may
have peaked in the late 1800s, a time when conditions across the
species' distribution were universally beneficial (Mayfield 1960, p.
32). Wildfires associated with intensive logging, agricultural burning,
and railroads in the Great Lakes region burned hundreds of thousands of
acres, and vast portions were dominated by jack pine forests (Pyne
1982, pp. 199-200, 214). Suitable winter habitat consisting of low
coppice (early-successional and dense, broadleaf vegetation) was also
becoming more abundant, due to a decrease in widespread commercial
agriculture in The Bahamas after the abolition of slavery in 1834,
resulting in former croplands converting to scrub (low coppice) (Sykes
and Clench 1998, p. 245). During this time, Kirtland's warblers were
found in greater abundance throughout The Bahamas than were found in
previous decades, and reports of migratory strays came from farther
north and west of the known migratory range, evidence of a larger
population that would produce more migratory strays (Mayfield 1993, p.
352).
Between the early 1900s and the 1920s, agriculture in the
northwoods was being discouraged in favor of industrial tree farming,
and systematic fire suppression was integrated into State and Federal
policy (Brown 1999, p. 9). Mayfield (1960, p. 26) estimated the amount
of jack pine on the landscape suitably aged for Kirtland's warblers had
decreased to approximately 40,470 ha (100,000 ac) of suitable habitat
in any one year. This reduction in habitat amount presumably resulted
in fewer Kirtland's warblers from the preceding time period, and
Kirtland's warblers were not observed in all stands of suitable
conditions (Wood 1904, p. 10). Serious efforts to control forest fires
in Michigan began in 1927, and resulted in a further reduction of total
acres burned, as the number of wildfires decreased and the size of
forest tracts that burned decreased (Mayfield 1960, p. 26; Radtke and
Byelich 1963, p. 210).
By this time, brown-headed cowbirds had expanded from the short
grass plains and become common within the Kirtland's warbler's nesting
range due to clearing of land for settlement and farming in northern
Michigan (Wood and Frothingham 1905, p. 49; Mayfield 1960, p. 146).
Brown-headed cowbirds are obligate brood parasites; females remove an
egg from a host species' nest and lay their own egg to be raised by the
adult hosts, and the result usually causes the death of the remaining
host nestlings (Rothstein 2004, p. 375). Brood parasitism by brown-
headed cowbirds contributed to the decline of Kirtland's warblers, and
a brown-headed cowbird trapping program was initiated in 1972, to
reduce the impact of brood parasitism (see Factor E discussion, below).
Comprehensive surveys (censuses) of the entire Kirtland's warbler
population began in 1951. Because of the warbler's specific habitat
requirements and the frequent, loud and persistent singing of males
during the breeding season, it was possible to establish a singing male
census (Ryel 1976, p. 2). The census consists of an extensive annual
survey of all known and potential breeding habitat to count singing
males. The census protocol assumes that there is a breeding female for
each singing male, so the number of singing males is assumed to equate
to the number of breeding pairs. Although this may not be true in some
cases, the census provides a robust, relative index of the Kirtland's
warbler population change over time (Probst et al. 2005, p. 51).
Censuses were conducted in 1951, 1961, each year from 1971 to 2013, and
in 2015 (Figure 1, below). The 1951 census documented a population of
432 singing males confined to 28 townships in eight counties in
northern lower Michigan (Mayfield 1953, p. 18). By 1971, the Kirtland's
warbler population declined to approximately 201 singing males and
[[Page 15764]]
was restricted to just 16 townships in six counties in northern lower
Michigan (Probst 1986, pp. 89-90). Over the next 18 years, the
Kirtland's warbler population level remained relatively stable at
approximately 200 singing males but experienced record lows of 167
singing males in 1974 and again in 1987. Shortly after 1987, the
population began a dramatic increase, reaching a record high of 2,383
singing males in 2015 (MDNR, USFS, USFWS unpubl. data).
Due in part to the increase in population numbers and distribution,
and significant effort and cost associated with monitoring for the
Kirtland's warbler, the census in Michigan's northern Lower Peninsula
has shifted to a less intensive survey protocol (Kennedy 2017, pers.
comm.; Williams et al. 2016, p. 1). Starting in 2017, surveys for
Kirtland's warblers in northern lower Michigan will occur every other
year in a portion of the known occupied habitat. This less intensive
survey is designed to detect population trends (Kennedy 2017, pers.
comm.).
[GRAPHIC] [TIFF OMITTED] TP12AP18.000
Since implementation of the brown-headed cowbird control program
began in 1972, the Kirtland's warbler population size closely tracked
with the amount of suitable habitat on the landscape in northern lower
Michigan at least through 2004 (Donner et al. 2008, p. 478). Overall,
the amount of suitable habitat increased by nearly 150 percent from
1979 to 2004. The source of suitable habitat began to shift during this
time as well. In the late 1980s, maturation of habitat generated
through wildfire composed a higher percentage of the total suitable
habitat available to the Kirtland's warbler compared to other types of
habitat (Donner et al. 2008, p. 472). By 1992, artificially regenerated
plantation habitat was nearly twice as abundant as wildfire habitat,
and increased to triple that of wildfire habitat by 2002 (Donner et al.
2008, p. 472). From 1979 to 1994, the majority of singing males were
found in wildfire-generated habitat (Donner et al. 2008, p. 474). By
1994, responding to a shift in available nesting habitat types, males
redistributed out of habitat generated by wildfire and unburned-
unplanted habitat and into plantation (planted) habitat. From 1995 to
2004, males continued redistributing into plantations from wildfire
habitat, and 85 percent of males were found in plantation habitat by
2004 (Donner et al. 2008, p. 475). This redistribution of males into
plantations also resulted in males being more evenly distributed across
the core breeding range than in
[[Page 15765]]
previous years. Artificial regeneration of suitable breeding habitat,
along with brown-headed cowbird control (as discussed under Factor E,
below), have been critical to the warbler's recovery, allowing for a
dramatic increase in population numbers and wider distribution across
the landscape. In general, increasing the amount, quality, and
distribution of available habitat results in larger, more genetically
diverse populations that are more resilient and can more readily
withstand perturbations (Shaffer and Stein 2000, pp. 308-312).
Population Viability
Brown et al. (2017a, p. 443) incorporated full annual cycle
(breeding and wintering) dynamics into a population viability model to
assess the long-term population viability of the Kirtland's warbler
under five management scenarios: (1) Current suitable habitat and
current cowbird removal; (2) reduced suitable habitat and current
cowbird removal; (3) current suitable habitat and reduced cowbird
removal, (4) current suitable habitat and no cowbird removal; and (5)
reduced suitable habitat and reduced cowbird removal. The model that
best simulated recently observed Kirtland's warbler population dynamics
included a relationship between precipitation in the species' wintering
grounds and productivity (Brown et al. 2017a, pp. 442, 444) that
reflects our understanding of carry-over effects (Rockwell et al. 2012,
pp. 748-750; Wunderle et al. 2014, pp. 46-48).
Under the current management conditions, which include habitat
management and brown-headed cowbird control at existing levels, the
model predicts that the Kirtland's warbler population will be stable
over a 50-year simulation period. When simulating a reduced brown-
headed cowbird removal effort by restricting cowbird trapping
activities to the central breeding areas in northern lower Michigan
(i.e., eastern Crawford County, southeastern Otsego County, Oscoda
County, western Alcona County, Ogemaw County, and Roscommon County) and
assuming a 41 percent or 57 percent reduction in Kirtland's warbler
productivity, the results showed a stable or slightly declining
population, respectively, over the 50-year simulation period (Brown et
al. 2017a, p. 447). Other scenarios, including reduced habitat
suitability and reduced Kirtland's warbler productivity due to
experimental jack pine management on 25 percent of available breeding
habitat, had similar results with projected population declines over
the 50-year simulation period, but mean population numbers remained
above the population goal of 1,000 pairs (Brown et al. 2017a, p. 446),
the numerical criterion identified in the Kirtland's warbler recovery
plan (USFWS 1985).
Brown et al. (2017a, p. 447) assumed that future reductions to the
Kirtland's warbler's productivity rates under two reduced cowbird
removal scenarios would be similar to historical rates. This assumption
would overestimate the negative effects on Kirtland's warbler
productivity if future parasitism rates are lower than the rates
modeled (see Factor E discussion, below, for additional information on
contemporary parasitism rates). Supplementary analysis (Brown et al.
2017b, unpub. report) using the model structure and assumptions of
Brown et al. (2017a) simulated the impacts of a 5, 10, 20, and 30
percent reduction in productivity to take into consideration a wider
range of possible future parasitism rates. Even small reductions in
annual productivity had measurable impacts on population abundance, but
there were not substantial differences in mean population growth rate
up to a 20 percent reduction in productivity (Brown et al. 2017b, p.
3). Even with annual reductions in productivity of up to 5 percent for
50 years, the population trend (growth rate) projected for the final 30
years of the model simulations was 0.998 (range from the 5 simulations
0.993 to 1.007) or nearly the same as that projected in the simulations
with no reduction in productivity at 0.999 (range of 0.995 to 1.008)
(Brown et al. 2017b, p. 3). It is reasonable to infer that the
Kirtland's warbler population can support relatively small reductions
in productivity over a long period of time (e.g., the 50-year timeframe
of the simulations), providing a margin of assurance as management
approaches are adaptively managed over time, and the species may be
able to withstand as great as a 20 percent reduction in annual
productivity, provided it does not extend over several years.
It is important to acknowledge that the results of the model
simulations are most helpful to indicate the effect of various
management decisions relative to one another, rather than provide
predictions of true population abundance. In other words, we
interpreted the model output to provide us with projections of relative
trends, rather than to apply specific population abundance thresholds
to each future projection. Although there are limitations to all
population models based on necessary assumptions, input data
limitations, and unknown long-term responses such as adaptation and
plasticity, data simulated by Brown et al. (2017a and 2017b, entire)
provide useful information in assessing relative population trends for
the Kirtland's warbler under a variety of future scenarios and provide
the best available analysis of population viability.
In summary, Kirtland's warbler population numbers have been greatly
affected by brown-headed cowbird parasitism rates and the extent and
quality of available habitat on the breeding grounds. The best
available population model predicts that limited non-traditional
habitat management and continued low brood parasitism rates will result
in sustained population numbers above the recovery goal. Monitoring
population numbers and brood parasitism rates will be important in
evaluating population viability in the future, and will be considered
as part of the post-delisting monitoring plan.
Recovery and Recovery Plan Implementation
State and Federal efforts to conserve the Kirtland's warbler began
in 1957, and were focused on providing breeding habitat for the
species. The Kirtland's warbler was federally listed as an endangered
species in 1967, under the Endangered Species Preservation Act of 1966
(Pub. L. 89-669). By 1972, a Kirtland's Warbler Advisory Committee had
been formed to coordinate management efforts and research actions
across Federal and State agencies, and conservation efforts expanded to
include management of brown-headed cowbird brood parasitism (Shake and
Mattsson 1975, p. 2).
Efforts to protect and conserve the Kirtland's warbler were further
enhanced when the Endangered Species Act of 1973 became law and
provided for acquisition of land to increase available habitat, funding
to carry out additional management programs, and provisions for State
and Federal cooperation. In 1975, the Kirtland's Warbler Recovery Team
(Recovery Team) was appointed by the Secretary of the Interior to guide
recovery efforts. A Kirtland's Warbler Recovery Plan was completed in
1976 (USFWS 1976), and updated in 1985 (USFWS 1985), outlining steps
designed to protect and increase the species' population.
Recovery plans provide important guidance to the Service, States,
and other partners on methods of minimizing threats to listed species
and measurable objectives against which to measure progress towards
recovery, but they are not regulatory documents. A decision to revise
the status of or remove a species from the List is ultimately based on
an analysis of the
[[Page 15766]]
best scientific and commercial data available to determine whether a
species is no longer an endangered species or a threatened species,
regardless of whether that information differs from the recovery plan.
The Kirtland's warbler recovery plan (USFWS 1985) identifies one
``primary objective'' (hereafter referred to as ``recovery criterion'')
that identifies when the species should be considered for removal from
the List, and ``secondary objectives'' (hereafter referred to as
``recovery actions'') that are designed to accomplish the recovery
criterion. The recovery criterion states that the Kirtland's warbler
may be considered recovered and considered for removal from the List
when a self-sustaining population has been re-established throughout
its known range at a minimum level of 1,000 pairs. The 1,000-pair
demography-based standard was informed by estimates of the amount of
the specific breeding habitat required by each breeding pair of
Kirtland's warblers, the amount of potential habitat available on
public lands in Michigan's northern Lower Peninsula, and the ability of
State and Federal land managers to provide suitable nesting habitat on
an annual basis. The recovery criterion was intended to address the
point at which the ultimate limiting factors to the species had been
ameliorated so that the population is no longer in danger of extinction
or likely to become so within the foreseeable future.
The recovery plan, however, does not clearly articulate how meeting
the recovery criterion will result in a population that is at reduced
risk of extinction. The primary threats to the Kirtland's warbler are
pervasive and recurring threats, but threat-based criteria specifying
measurable targets for control or reduction of those threats were not
incorporated into the recovery plan. Instead, the recovery plan lists
actions focused on specific actions, in order to accomplish the
recovery criterion. These included managing breeding habitat,
protecting the Kirtland's warbler on its wintering grounds and along
the migration route, reducing key factors such as brown-headed cowbird
parasitism from adversely affecting reproduction and survival of
Kirtland's warblers, and monitoring the Kirtland's warbler to evaluate
responses to management practices and environmental changes.
At the time the recovery plan was prepared, we estimated that land
managers would need to annually maintain approximately 15,380 ha
(38,000 ac) of nesting habitat in order to support and sustain a
breeding population of 1,000 pairs (USFWS 1985, pp. 18-20). We
projected that this would be accomplished by protecting existing
habitat, improving occupied and developing habitat, and establishing
approximately 1,010 ha (2,550 ac) of new habitat each year, across
51,640 ha (127,600 ac) of State and Federal pine lands in the northern
Lower Peninsula of Michigan (USFWS 1985, pp. 18-20). We also
prioritized development and improvement of guidelines that would
maximize the effectiveness and cost efficiency of habitat management
efforts (USFWS 1985, p. 24). The MDNR, USFS, and Service developed the
Strategy for Kirtland's Warbler Habitat Management (Huber et al. 2001,
entire) to update Kirtland's warbler breeding habitat management
guidelines and prescriptions based on a review of past management
practices, analysis of current habitat conditions, and new findings
that would continue to conserve and enhance the status of the
Kirtland's warbler (Huber et al. 2001, p. 2).
By the time the recovery plan was updated in 1985, the brown-headed
cowbird control program had been in effect for more than 10 years. The
brown-headed cowbird control program had virtually eliminated brood
parasitism and more than doubled the warbler's productivity rates in
terms of fledging success (Shake and Mattsson 1975, pp. 2-4). The
Kirtland's warbler's reproductive capability had been successfully
restored, and the brown-headed cowbird control program was credited
with preventing further decline of the species. Because management of
brown-headed cowbird brood parasitism was considered essential to the
survival of the Kirtland's warbler, it was recommended that the brown-
headed cowbird control program be maintained for ``as long as
necessary'' (USFWS 1985, p. 27).
Although the recovery plan identifies breeding habitat as the
primary limiting factor, with brood parasitism as a secondary limiting
factor, it also suggests that events or factors outside the breeding
season might be adversely affecting survival (USFWS 1985, pp. 12-13).
At the time the recovery plan was updated, little was known about the
Kirtland's warbler's migratory and wintering behavior, the species'
migratory and wintering habitat requirements, or ecological changes
that may have occurred within the species' migration route or on its
wintering range. This lack of knowledge emphasized a need for more
information on the Kirtland's warbler post fledging, during migration,
and on its wintering grounds (Kelly and DeCapita 1982, p. 365).
Accordingly, recovery efforts were identified to: (1) Define the
migration route and locate wintering areas, (2) investigate the ecology
of the Kirtland's warbler and factors that might be affecting mortality
during migration and on its winter range, and (3) provide adequate
habitat and protect the Kirtland's warbler during migration and on its
wintering areas (USFWS 1985, pp. 24-26).
In correspondence with the Service's Midwest Regional Director, and
based on more than 20 years of research on the Kirtland's warbler's
ecology and response to recovery efforts, the Recovery Team helped
clarify recovery progress and issues that needed attention prior to
reclassification to threatened status or delisting (Ennis 2002, pp. 1-
4; Ennis 2005, pp. 1-3). From that synthesis, several important
concepts emerged that continued to inform recovery including: (1)
Breeding habitat requirements, amount, configuration, and distribution;
(2) brood parasitism management; (3) migratory connectivity, and
protection of Kirtland's warblers and their habitat during migration
and on the wintering grounds; and (4) establishment of credible
mechanisms to ensure the continuation of necessary management (Thorson
2005, pp. 1-2).
Our understanding of the Kirtland's warbler's breeding habitat
selection and use and the links between maintaining adequate amounts of
breeding habitat and a healthy Kirtland's warbler population has
continued to improve. As the population has rebounded, Kirtland's
warblers have become reliant on artificial regeneration of breeding
habitat, but have also recolonized naturally regenerated areas within
the historical range of the species and nested in habitat types
previously considered non-traditional or less suitable. As explained in
more detail below, recovery efforts have expanded to establish and
enhance management efforts on the periphery of the species' current
breeding range in Michigan's Upper Peninsula, Wisconsin, and Canada,
and reflect the best scientific understanding of the amount and
configuration of breeding habitat (see Factor A discussion, below).
These adjustments improve the species' ability to adapt to changing
environmental conditions, withstand stochastic disturbance and
catastrophic events, and better ensure long-term conservation for the
species.
The brown-headed cowbird control program has run uninterrupted
since 1972, as recommended in the recovery plan, and the overall
methodology has remained largely unchanged since the
[[Page 15767]]
program was established. Along with habitat management, brown-headed
cowbird control has proven to be a very effective tool in stabilizing
and increasing the Kirtland's warbler population. To ensure survival of
the Kirtland's warbler, we anticipate that continued brown-headed
cowbird brood parasitism management may be needed, at varying levels
depending on parasitism rates, to sustain adequate Kirtland's warbler
productivity. As explained in more detail below, brown-headed cowbird
control techniques and the scale of trapping efforts have adapted over
time and will likely continue to do so, in order to maximize program
effectiveness and feasibility (see Factor E discussion, below).
We now recognize that the Kirtland's warbler persists only through
continual management activities designed to mitigate recurrent threats
to the species. The Kirtland's warbler is considered a conservation-
reliant species, which means that it requires continuing management to
address ongoing threats (Goble et al. 2012, p. 869). Conservation of
the Kirtland's warbler will continue to require a coordinated, multi-
agency approach for planning and implementing conservation efforts into
the future. Bocetti et al. (2012, entire) used the Kirtland's warbler
as a case study on the challenge of delisting conservation-reliant
species. They recommended four elements that should be in place prior
to delisting a conservation-reliant species, including a conservation
partnership capable of continued management, a conservation plan,
appropriate binding agreements (such as memoranda of agreement (MOAs))
in place, and sufficient funding to continue conservation actions into
the future (Bocetti et al. 2012, p. 875).
The Kirtland's warbler has a strong conservation partnership
consisting of multiple stakeholders that have invested considerable
time and resources to achieving and maintaining this species' recovery.
Since 2016, the Recovery Team is no longer active, but instead new
collaborative efforts formed to help ensure the long-term conservation
of the Kirtland's warbler regardless of its status under the Act. These
efforts formed to facilitate conservation planning through
coordination, implementation, monitoring, and research efforts among
many partners and across the species' range. A coalition of
conservation partners lead by Huron Pines, a nonprofit conservation
organization based in northern Michigan, launched the Kirtland's
Warbler Initiative in 2013. The Kirtland's Warbler Initiative brings
together State, Federal, and local stakeholders to identify and
implement strategies to secure funds for long-term Kirtland's warbler
conservation actions given the continuous, recurring costs anticipated
with conserving the species into the future. The goal of this
partnership is to ensure the Kirtland's warbler thrives and ultimately
is delisted, as a result of strong public-private funding and land
management partnerships. Through the Kirtland's Warbler Initiative, a
stakeholder group called the Kirtland's Warbler Alliance was developed
to raise awareness in support of the Kirtland's warbler and the
conservation programs necessary for the health of the species and jack
pine forests.
The second effort informing Kirtland's warbler conservation efforts
is the Kirtland's Warbler Conservation Team. The Kirtland's Warbler
Conservation Team was established to preserve institutional knowledge,
share information, and facilitate communication and collaboration among
agencies and partners to maintain and improve Kirtland's warbler
conservation. The current Kirtland's Warbler Conservation Team is
comprised of representatives from the Service, USFS, MDNR, Wisconsin
DNR, U.S. Department of Agriculture's Wildlife Services (USDA-WS),
Canadian Wildlife Service, Huron Pines, Kirtland's Warbler Alliance,
The Nature Conservancy, and California University of Pennsylvania.
Since 2015, conservation efforts for the Kirtland's warbler have
been guided by the Kirtland's Warbler Breeding Range Conservation Plan
(Conservation Plan) (MDNR et al. 2015, https://www.michigan.gov/documents/dnr/Kirtlands_Warbler_CP_457727_7.pdf). The Conservation Plan
outlines the strategy for future cooperative Kirtland's warbler
conservation and provides technical guidance to land managers and
others on how to create and maintain Kirtland's warbler breeding
habitat within an ecosystem management framework. The scope of the
Conservation Plan currently focuses only on the breeding range of the
Kirtland's warbler within the United States, although the agencies
involved (MDNR, USFS, and USFWS) intend to cooperate with other
partners to expand the scope of the plan in the future to address the
entire species' range (i.e., the entire jack pine ecosystem, as well as
the migratory route and wintering range of the species). The
Conservation Plan will be revised every 10 years to incorporate any new
information and the best available science (MDNR et al. 2015, p. 1).
In April 2016, the Service, MDNR, and USFS renewed a memorandum of
understanding (MOU) committing the agencies to continue collaborative
habitat management, brown-headed cowbird control, monitoring, research,
and education in order to maintain the Kirtland's warbler population at
or above 1,000 breeding pairs, regardless of the species' legal
protection under the Act (USFWS, MDNR, and USFS 2016, entire). In
addition, Kirtland's warbler conservation actions are included in the
USFS's land and resource management plans (Forest Plans), which guide
management priorities for the Huron-Manistee, Hiawatha, and Ottawa
National Forests.
Funding mechanisms that support long-term land management and
brown-headed cowbird control objectives are in place to assure a high
level of certainty that the agencies can meet their commitments to the
conservation of the Kirtland's warbler. MDNR and USFS have replanted
approximately 26,420 ha (90,000 ac) of Kirtland's warbler habitat over
the past 30 years. Over the last 10 years, only a small proportion of
the funding used to create Kirtland's warbler habitat is directly tied
to the Act through the use of grant funding (i.e., section 6 funding
provided to the MDNR). Although there is the potential that delisting
could reduce the priority for Kirtland's warbler work within the MDNR
and USFS, as noted in the Conservation Plan (MDNR 2015, p. 17), much of
the forest management cost (e.g., silvicultural examinations, sale
preparation, and reforestation) is not specific to maintaining
Kirtland's warbler breeding habitat and would likely be incurred in the
absence of the Kirtland's warbler. The MDNR and USFS have successfully
navigated budget shortfalls and changes in funding sources over the
past 30 years and were able to provide sufficient breeding habitat to
enable the population to recover, and have agreed to continue to do so
through the MOU. Additionally, the Service and MNDR developed an MOA to
set up a process for managing funds to help address long-term
conservation needs, specifically brown-headed cowbird control (USFWS
and MDNR 2015, entire). If the annual income generated is greater than
the amount needed to manage brown-headed cowbird parasitism rates, the
remaining portion of the annual income may be used to support other
high priority management actions to directly benefit the Kirtland's
warbler, including wildlife and habitat management, land acquisition
and consolidation, and education. The MOA
[[Page 15768]]
requires that for a minimum of 5 years after the species is delisted,
MDNR consult with the Service on planning the annual brown-headed
cowbird control program and other high priority actions. In addition,
MDNR recently reaffirmed their commitment to the MOA and confirmed
their intent to implement and administer the brown-headed cowbird
control program, even if the Kirtland's warbler is delisted (MDNR
2017).
In summary, the general guidance of the recovery plan has been
effective, and the Kirtland's warbler has responded well to active
management over the past 50 years. The primary threats identified at
listing and during the development of the recovery plan have been
managed, and commitments are in place to continue managing the threats.
The status of the Kirtland's warbler has improved, primarily due to
breeding habitat and brood parasitism management provided by MDNR,
USFS, and the Service. The population has been above the 1,000 pair
goal since 2001, above 1,500 pairs since 2007, and above 2,000 pairs
since 2012. The recovery criterion has been met. Since 2015, efforts
for the Kirtland's warbler have been guided by a Conservation Plan that
will continue to be implemented if the species is delisted.
Since the revision of the recovery plan (USFWS 1985), decades of
research have been invaluable to refining recovery implementation and
have helped clarify our understanding of the dynamic condition of the
Kirtland's warbler, jack pine ecosystem, and the factors influencing
them. The success of recovery efforts in mitigating threats to the
Kirtland's warbler are evaluated below.
Summary of Factors Affecting the Kirtland's Warbler
Section 4 of the Act and its implementing regulations (50 CFR part
424) set forth the procedures for listing species, reclassifying
species, or removing species from listed status. The term ``species''
includes ``any subspecies of fish or wildlife or plants, and any
distinct population segment [DPS] of any species of vertebrate fish or
wildlife which interbreeds when mature'' (16 U.S.C. 1532(16)). A
species may be determined to be an endangered species or threatened
species because of any one or a combination of the five factors
described in section 4(a)(1) of the Act: (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 must consider these same five
factors in delisting a species. We may delist a species according to 50
CFR 424.11(d) if the best available scientific and commercial data
indicate that the species is neither endangered nor threatened for the
following reasons: (1) The species is extinct; (2) the species has
recovered and is no longer endangered or threatened; and/or (3) the
original scientific data used at the time the species was classified
were in error.
For species that are already listed as endangered or threatened,
this analysis of threats is an evaluation of both the threats currently
facing the species and the threats that are reasonably likely to affect
the species in the foreseeable future following delisting or
downlisting (i.e., reclassification from endangered to threatened) and
the removal or reduction of the Act's protections. A recovered species
is one that no longer meets the Act's definition of endangered or
threatened. A species is ``endangered'' for purposes of the Act if it
is in danger of extinction throughout all or a ``significant portion of
its range'' and is ``threatened'' if it is likely to become endangered
within the foreseeable future throughout all or a ``significant portion
of its range.'' The word ``range'' in the ``significant portion of its
range'' phrase refers to the range in which the species currently
exists. For the purposes of this analysis, we will evaluate whether the
currently listed species, the Kirtland's warbler, should be considered
endangered or threatened throughout all of its range. Then we will
consider whether there are any significant portions of the Kirtland's
warbler's range where the species is in danger of extinction or likely
to become so within the foreseeable future.
The Act does not define the term ``foreseeable future.'' For the
purpose of this proposed rule, we defined the ``foreseeable future'' to
be the extent to which, given the amount and substance of available
data, we can anticipate events or effects, or reliably extrapolate
threat trends, such that we reasonably believe that reliable
predictions can be made concerning the future as it relates to the
status of the Kirtland's warbler. Based on the history of habitat and
brown-headed cowbird management and the established commitment by State
and Federal partners to continue the necessary management that has been
conducted over the past 50 years, as well as the predictions of the
population viability model (Brown et al. 2017a, entire) that considers
a 50-year timeframe into the future, it is reasonable to define the
foreseeable future for the Kirtland's warbler as 50 years. Beyond that
time period, the future conditions become more uncertain, such that we
cannot make predictions as to how they will affect the status of the
species.
In considering what factors might constitute threats, we must look
beyond the exposure of the species to a particular factor to evaluate
whether the species may respond to the factor in a way that causes
actual impacts to the species. If there is exposure to a factor and the
species responds negatively, the factor may be a threat, and during the
status review, we attempt to determine how significant a threat it is.
The threat is significant if it drives or contributes to the risk of
extinction of the species, such that the species warrants listing as
endangered or threatened as those terms are defined by the Act.
However, the identification of factors that could impact a species
negatively may not be sufficient to compel a finding that the species
warrants listing. The information must include evidence sufficient to
suggest that the potential threat is likely to materialize and that it
has the capacity (i.e., it should be of sufficient magnitude and
extent) to affect the species' status such that it meets the definition
of endangered or threatened under the Act. The following analysis
examines all five factors currently affecting or that are likely to
affect the Kirtland's warbler in the foreseeable future.
A. The Present or Threatened Destruction, Modification or Curtailment
of Its Habitat or Range
Breeding Habitat
Historically, wildfires were the most important factor in the
establishment of natural jack pine forests and Kirtland's warbler
breeding habitat. However, modern wildfire suppression greatly altered
the natural disturbance regime that generated Kirtland's warbler
breeding habitat for thousands of years (USFWS 1985, p. 12; Cleland et
al. 2004, pp. 316-318). Prior to the 20th century, the historic fire
recurrence in jack pine forests averaged 59 years; although it is now
estimated to occur in cycles as long as 775 years (Cleland et al. 2004,
pp. 315-316).
In the absence of wildfire, land managers must take an active role
in mimicking natural processes that regularly occurred within the jack
pine ecosystem, namely stand-replacing disturbance events. This is
primarily done through large-scale timber harvesting and human-assisted
reforestation. Although planted stands
[[Page 15769]]
tend to be more structurally simplified than wildfire-regenerated
stands (Spaulding and Rothstein 2009, p. 2610), land managers have
succeeded in selecting Kirtland's Warbler Management Areas that have
landscape features of the natural breeding habitat and have developed
silvicultural techniques that produce conditions within planted stands
suitable for Kirtland's warbler nesting. In fact, over 85 percent of
the habitat used by breeding Kirtland's warblers in 2015 in the
northern Lower Peninsula of Michigan (approximately 12,343 ha (30,500
ac)) had been artificially created through clearcut harvest and
replanting. The planted stands supported over 92 percent of the
warbler's population within the Lower Peninsula during the breeding
season (MDNR, USFS, USFWS, unpubl. data). The effectiveness of these
strategies is also evident by the reproductive output observed in
planted stands, which function as population sources (Bocetti 1994, p.
95). Thus, in a landscape where natural fire disturbance patterns have
been reduced, threats to natural breeding habitat are being mitigated
through large-scale habitat management. Therefore, the status of the
Kirtland's warbler depends largely on the continued production of
managed breeding habitat.
The Conservation Plan (MDNR et al. 2015) identifies continued
habitat management needs and objectives to maintain sufficient suitable
breeding habitat for Kirtland's warblers. Habitat management is
currently conducted on approximately 88,626 ha (219,000 ac) of jack
pine forest within MDNR, USFS, and Service lands throughout the
northern Lower Peninsula and Upper Peninsula of Michigan (MDNR et al.
2015, pp. 22-23). The Conservation Plan incorporates some conservative
assumptions about the area needed to support a breeding pair of
Kirtland's warblers, as well as how long a stand will be used by the
species. The density and duration of use estimates were developed by
data gathered over the last decade. Lands within the Lower Peninsula
averaged 8 to 9 ha (19 to 22 ac) per pair and had a duration of use
between 9 and 10 years. Lands within the Upper Peninsula on the
Hiawatha National Forest required an average of 40 ha (100 ac) per pair
and had a duration of use averaging 10 years (Huber et al. 2013 cited
in MDNR et al. 2015, p. 22). Using those measures of average hectares
per pair and duration of use, 14,593 ha (36,060 ac) of suitable
breeding habitat would need to be available at all times to maintain a
minimum population of 1,300 pairs, requiring land management agencies
to jointly manage 1,550 ha (3,830 ac) of habitat annually (631 ha
(1,560 ac) on MDNR land and 918 ha (2,270 ac) on USFS land) through
wildfire-regenerated jack pine or managed reforestation (MDNR et al.
2015, pp. 22-23). It is important to recognize that the more recent
observations concerning density of Kirtland's warblers in breeding
habitat and duration of stand use are often greater than the
assumptions used for planning purposes and explain why the Kirtland's
warbler population that is actually observed is higher than would be
predicted based on the planning assumptions.
The Conservation Plan identifies a goal to develop at least 75
percent of the Kirtland's warbler's breeding habitat acreage using
traditional habitat management techniques (opposing wave planting with
interspersed openings), and no more than 25 percent of habitat using
non-traditional habitat management techniques (e.g., reduced stocking
density, incorporating a red pine component within a jack pine stand,
prescribed burning) (MDNR et al. 2015, p. 23). Non-traditional
techniques will be used to evaluate new planting methods that improve
timber marketability, reduce costs, and improve recreational
opportunities while sustaining the warbler's population above the
recovery criterion of 1,000 pairs. The majority of managed breeding
habitat is created through clear cutting and planting jack pine
seedlings. However, managing jack pine for Kirtland's warbler breeding
habitat typically results in lower value timber products due to the
overall poor site quality in combination with the required spacing,
density, and rotation age of the plantings (Greco 2017, pers. comm.).
Furthermore, the demand for jack pine products has fluctuated in recent
years, and long-term forecasts for future marketability of jack pine
are uncertain. Commercially selling jack pine timber on sites where
reforestation will occur is critical to the habitat management program.
Timber receipts offset the cost of replanting jack pine at the
appropriate locations, scales, arrangements, and densities needed to
support a viable population of nesting Kirtland's warblers that would
not otherwise be feasible through conservation dollars. The Kirtland's
Warbler Conservation Team is currently working on developing techniques
through adaptive management that increase the marketability of the
timber at harvest while not substantially reducing Kirtland's warbler
habitat suitability (Dan Kennedy 2017, pers. comm.).
The land management agencies have maintained adequate breeding
habitat despite times when their budgets were flat or declining, even
while costs related to reforestation continue to increase. For example,
over the last 30 years, the MDNR replanted over 20,000 ha (50,000 ac)
of Kirtland's warbler habitat, averaging over 680 ha (1,700 ac) per
year. They took this action voluntarily, and within the past 10 years,
they used funding from sources other than those available under the
Act. Section 6 grants under the Act have helped support MDNR's
Kirtland's warbler efforts, but that funding has largely been used for
population census work in recent years and reflects only a small
percentage of the funding the State of Michigan spends annually to
produce Kirtland's warbler breeding habitat.
Shifting agency priorities and competition for limited resources
have and will continue to challenge the ability of land managers to
fund reforestation of areas suitable for Kirtland's warblers. Low jack
pine timber sale revenues, in conjunction with reduced budgets,
increased Kirtland's warbler habitat reforestation costs, and
competition with other programs, are challenges the land management
agencies have met in the past and will need to continue addressing to
meet annual habitat development objectives. Commitments by land
managers and the Conservation Team are in place, as described
previously, to ensure recovery of the Kirtland's warbler will be
sustained despite these challenges.
A regulatory mechanism that aids in the management of breeding
habitat is Executive Order (E.O.) 13186, ``Responsibilities of Federal
Agencies to Protect Migratory Birds'' (66 FR 3853), which directs
Federal agencies to develop a memorandum of understanding (MOU) with
the Service to promote the conservation of migratory bird populations.
The USFS and the Service signed an MOU (FS Agreement #08-MU-1113-2400-
264) pursuant to E.O. 13186 with the purpose of strengthening migratory
bird conservation by identifying and implementing strategies that
promote conservation and avoid or minimize adverse impacts on migratory
birds through enhanced collaboration. Additionally, USFS Forest Plans
have been developed in compliance with the provisions of section 7 of
the Act and the Healthy Forest Restoration Act of 2003 (Pub. L. 108-
148). These plans emphasize management that maintains
[[Page 15770]]
and develops essential breeding habitat for the Kirtland's warbler
(USFS 2006a, p. 82; USFS 2006b, p. 35).
We reviewed available information on the effects from expanded
development adjacent to occupied habitats in both breeding and
wintering areas, and impacts from recreational activities on the
breeding grounds. Although these factors and those discussed above do
affect Kirtland's warblers and their habitat, land management agencies
have been successful in maintaining sufficient amounts of suitable
habitat to support historically high numbers of Kirtland's warblers.
Although activities that affect breeding habitat may still have some
negative effects on individual Kirtland's warblers, the population of
Kirtland's warblers appears resilient to these activities within the
context of the current management regime. Furthermore, to date,
management efforts have been adaptive in terms of the acreage and
spatial and temporal configuration of habitat needed to mitigate the
effects associated with natural breeding habitat loss and
fragmentation. The land management agencies have shown a commitment to
Kirtland's warbler habitat management through signing the 2016 MOU,
agreeing to continue habitat management, and developing and
implementing the Conservation Plan.
Migration Habitat
Although Kirtland's warblers spend a relatively small amount of
time each year migrating, the migratory period has the highest
mortality rate out of any phase of the annual cycle, accounting for 44
percent of annual mortality (Rockwell et al. 2017, p. 722). Migratory
survivorship levels are, however, above the minimum needed to sustain
the population (Mayfield 1960, pp. 204-207; Berger and Radabaugh 1968,
p. 170; Bocetti et al. 2002, p. 99; Rockwell et al. 2017, pp. 721-723;
Trick, unpubl data). Recent research is refining our knowledge of
spring and fall migration timing and routes for the Kirtland's warbler.
Little is currently known about the importance of specific stop-over
sites and any factors affecting them, although coastal areas along the
Great Lakes and Atlantic Ocean (e.g., western Lake Erie basin and the
Florida and Georgia coasts) that appear important to migrating
Kirtland's warblers are also areas where natural habitats have been
highly fragmented by human development. At stopover sites within these
highly fragmented landscapes, competition for food sources among long-
distance passerine migrants is expected to be high, especially in
fallout areas (when many migrating birds land to rest, usually due to
weather events or long flights over open water, Moore and Yong 1991,
pp. 86-87; Kelly et al. 2002, p. 212; N[eacute]meth and Moore 2007, p.
373), and may prolong stopover duration or increase the number of
stopovers that are needed to complete migration between breeding and
wintering grounds (Goymann et al. 2010, p. 480).
The quantity and quality of migratory habitat needed to sustain
Kirtland's warbler numbers above the recovery goal of 1,000 pairs
appears to be sufficient, based on a sustained and increasing
population since 2001. If loss or destruction of migratory habitat were
limiting or likely to limit the population to the degree that
maintaining a healthy population may be at risk, it should be apparent
in the absence of the species from highly suitable breeding habitat in
the core breeding range. In fact, we have seen just the opposite:
Increasing densities of breeding individuals in core areas and a range
expansion into what would appear to be less suitable habitat elsewhere.
This steady population growth and range expansion has occurred despite
increased development and fragmentation of migratory stopover habitat
within coastal areas; therefore, loss or degradation of migratory
habitat is not a substantial threat to the species now or in the
foreseeable future.
Wintering Habitat
The quantity and quality of wintering habitat needed to sustain
Kirtland's warbler numbers above the recovery goal of 1,000 pairs
appears to be sufficient, based on a sustained and increasing
population since 2001. Compared to the breeding grounds, less is known
about the wintering grounds in The Bahamas. Factors affecting
Kirtland's warblers on the wintering grounds, as well as the magnitude
of the impacts, remain somewhat uncertain. Few of the known Kirtland's
warbler wintering sites currently occur on protected land. Rather, most
Kirtland's warblers appear to winter more commonly in early
successional habitats that have recently been or are currently being
used by people (e.g., abandoned after clearing, grazed by goats), where
disturbance has set back plant succession (Wunderle et al. 2010, p.
132). Potential threats to wintering habitat include habitat loss
caused by human development, altered fire regime, changes in
agricultural practices, and invasive plant species. The potential
threats of rising sea level, drought, and destructive weather events
such as hurricanes on the wintering grounds are discussed below under
Factor E.
Tourism is the primary economic activity in The Bahamas, accounting
for 65 percent of the gross domestic product, and The Bahamas' Family
Islands Development Encouragement Act of 2008 supports the development
of resorts on each of the major Family Islands (part of The Bahamas)
(Moore and Gape 2009, p. 72). Residential and commercial development
could result in direct loss of Kirtland's warbler habitat, especially
on New Providence and Grand Bahama, which together support 85 percent
of the population of Bahamian people (Moore and Gape 2009, p. 73;
Wunderle et al. 2010, p. 135; Ewert 2011, pers. comm.). This loss could
occur on both private and commonage lands (land held communally by
rural settlements), as well as generational lands (lands held jointly
by various family members).
Local depletion and degradation of the water table from wells and
other water extraction and introduction of salt water through human-
made channels or other disturbances to natural hydrologies may also
negatively impact Kirtland's warblers by affecting fruit and arthropod
availability (Ewert 2011, pers. comm.).
Fire may have positive or negative impacts on winter habitat,
depending on the frequency and intensity of fires, and where the fires
occur. Fires are relatively common and widespread on the pine islands
in the northern part of the archipelago, and have increased since
settlement, especially during the dry winter season when Kirtland's
warblers are present (The Nature Conservancy 2004, p. 3). Human-made
fires may negatively impact wintering Kirtland's warblers if they
result in reduced density and fruit production of understory shrubs in
Caribbean pine (Pinus caribaea) stands (Lee et al. 1997, p. 27; Currie
et al. 2005b, p. 85). On non-pine islands, fire may benefit Kirtland's
warblers when succession of low coppice to tall coppice is set back
(Currie et al. 2005b, p. 79).
Invasive plants are another potential factor that could limit the
extent of winter habitat in The Bahamas. Brazilian pepper (Schinus
terebinthifolius), jumbie bean (Leucaena leucocephala), and Guinea
grass (Panicum maximum) may be the most important invasive species of
immediate concern (Ewert 2011, pers. comm.). These aggressive plants
colonize patches early after disturbances and may form monocultures,
which preclude the establishment of species heavily used by Kirtland's
warblers. Some invasive species, such as jumbie bean, are good forage
for goats. By browsing on these invasive plants, goats
[[Page 15771]]
create conditions that favor native shrubs and may increase the density
of native shrubs used by Kirtland's warblers (Ewert 2011, pers. comm.).
Goat farming could play a role in controlling the spread of some
invasive species at a local scale, while aiding in the restoration of
native vegetation patches. Still, many plants such as royal poinciana
(Delonix regia), tropical almond (Terminalia catappa), and morning
glory (Ipomoea indica) are commonly imported for landscaping and have
the potential to escape into the wild and become invasive (Smith 2010,
pp. 9-10; Ewert 2011, pers. comm.).
The Bahamas National Trust administers 32 national parks that cover
over 809,371 ha (2 million ac) (Bahamas National Trust 2017, p. 3).
Although not all national parks contain habitat suitable for Kirtland's
warblers, several parks are known to provide suitable wintering
habitat, including the Leon Levy Native Plant Preserve on Eleuthera
Island, Harrold and Wilson Ponds National Park on New Providence
Island, and Exuma Cays Land and Sea Park on Hawksbill Cay (The Nature
Conservancy 2011, p. 2). Hog Bay Island, a national park in Bermuda,
also provides suitable Kirtland's warbler wintering habitat (Amos
2005).
Caribbean pine, a potentially important component of wintering
Kirtland's warbler habitat, is protected from harvest in The Bahamas
under the Conservation and Protection of the Physical Landscape of The
Bahamas (Declaration of Protected Trees) Order of 1997. The Bahamas
National Trust Act of 1959 and the National Parks Ordinance of 1992
established non-government statutory roles to the Bahamas National
Trust and the Turks and Caicos Islands National Trust, respectively.
These acts empower these organizations to hold and manage
environmentally important lands in trust for their respective
countries.
Simply protecting parcels of land or important wintering habitat,
however, may be insufficient to sustain adequate amounts of habitat for
the Kirtland's warbler because of the species' dependence on early
successional habitat (Mayfield 1972, p. 349; Sykes and Clench 1998, pp.
256-257; Haney et al. 1998, p. 210; Wunderle et al. 2010, p. 124),
which changes in distribution over time. In addition, food availability
at any one site varies seasonally, as well as between years, and is not
synchronous across all sites (Wunderle et al. 2010, p. 124). In the
face of changes in land use and availability, sustaining sufficient
patches of early-successional habitat for Kirtland's warbler in The
Bahamas will likely require a landscape-scale approach (Wunderle et al.
2010, p. 135).
Although threats to Kirtland's warblers on the wintering grounds
exist as a result of habitat loss due to succession or development, the
current extent and magnitude of these threats appears not to be
significantly limiting Kirtland's warbler population numbers based on
the species' continuous population growth over the last two decades.
This indicates that loss or degradation of winter habitat is not a
substantial threat causing population-level effects to the species now
or in the foreseeable future.
Habitat Distribution
The Kirtland's warbler has always occupied a relatively limited
geographic range on both the breeding and wintering grounds. This
limited range makes the species naturally more vulnerable to
catastrophic events compared to species with wide geographic
distributions, because having multiple populations in a wider
distribution reduces the likelihood that all individuals will be
affected simultaneously by a catastrophic event (e.g., large wildfire
in breeding habitat, hurricane in The Bahamas). Since the species was
listed, the geographic area where the Kirtland's warbler occurs has
increased, reducing the risk to the species from catastrophic events.
As the population continues to increase and expand in new breeding and
wintering areas, the species will become less vulnerable to
catastrophic events. The Conservation Plan, which land management
agencies agreed to implement under the 2016 MOU, includes a goal to
improve distribution of habitat across the breeding range to reduce
this risk by managing lands in the Upper Peninsula of Michigan and in
Wisconsin in sufficient quantity and quality to provide breeding
habitat for 10 percent (100 pairs) or more of the 1,000 pairs goal
(MDNR et al. 2015, p. 23).
B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
The Kirtland's warbler is a non-game species, and there is no known
or potential commercial harvest in either the breeding or wintering
grounds. Utilization for recreational, scientific, or educational
purposes appears to be adequately regulated by several State, Federal,
and international wildlife laws, based on a sustained and increasing
population since 2001. Land management agencies within the Kirtland's
warbler's breeding range have the ability to implement seasonal
closures to specific areas for a variety of reasons and, when
necessary, could limit access outside of designated roads and trails to
further protect the species.
The Kirtland's warbler is protected by the Migratory Bird Treaty
Act of 1918 (MBTA; 16 U.S.C. 703-712). The MBTA prohibits take,
capture, killing, trade, or possession of Kirtland's warblers and their
parts, as well as their nests and eggs. The regulations implementing
the MBTA further define ``take'' as to ``pursue, hunt, shoot, wound,
kill, trap, capture, or collect'' or attempt those activities (50 CFR
10.12).
The States of Florida, Georgia, Indiana, Michigan, North Carolina,
Ohio, Virginia, and Wisconsin list the Kirtland's warbler as
endangered, under their respective State endangered species
regulations. In Michigan, where the majority of the population breeds,
part 365 of Public Act 451 of 1994 prohibits take, possession,
transportation, importation, exportation, processing, sale, offer for
sale, purchase, or offer to purchase, transportation or receipt for
shipment by a common or contract carrier of Kirtland's warblers or
their parts. The Kirtland's warbler is listed as endangered under
Ontario's Endangered Species Act of 2007.
The Kirtland's warbler was declared federally endangered in Canada
in 1979. Canada's Species at Risk Act of 2003 (SARA) is the primary law
protecting the Kirtland's warbler in Canada. Canada's SARA bans
killing, harming, harassing, capturing, taking, possessing, collecting,
buying, selling, or trading of individuals that are federally listed.
In addition, SARA also extends protection to the residence (habitat) of
individuals that are federally listed.
Canada's Migratory Bird Convention Act of 1994 also provides
protections to Kirtland's warblers. Under Canada's Migratory Bird
Convention Act, it is unlawful to be in possession of migratory birds
or nests, or to buy, sell, exchange, or give migratory birds or nests,
or to make them the subject of commercial transactions.
In The Bahamas and the Turks and Caicos Islands, the Kirtland's
warbler is recognized as a globally Near Threatened species, but has no
federally listed status. In The Bahamas, the Wild Birds Protection Act
(chapter 249) allows the Minister of Wild Animals and Birds Protection
to establish and modify reserves for the protection of any wild bird.
The species is also protected in The Bahamas by the Wild Animals
(Protection) Act (chapter 248) that prohibits the take or capture,
export, or attempt to take, capture, or export any wild animal from The
Bahamas. The Bahamas regulates scientific utilization
[[Page 15772]]
of the Kirtland's warbler, based on recommendations previously provided
by the Kirtland's Warbler Recovery Team (Bocetti 2011, pers. comm.).
The species remains protected from pursuit, wounding, or killing
that could potentially result from activities focused on the species in
breeding, wintering, and migratory habitat (e.g., wildlife photography
without appropriate care to ensure breeding birds can continue to feed
and care for chicks and eggs normally and without injury to their
offspring). Overutilization for recreational, scientific, or
educational purposes does not constitute a substantial threat to the
Kirtland's warbler now or in the foreseeable future.
C. Disease or Predation
There is no information of any disease impacting the Kirtland's
warbler on either the breeding or wintering grounds.
For most passerines, nest predation has the greatest negative
impact on reproductive success, and can affect entire populations
(Ricklefs 1969, p. 6; Martin 1992, p. 457). Nest predation may be
particularly detrimental for ground-nesting bird species in shrublands
(Martin 1993, p. 902). Predation rates of Kirtland's warbler nests have
ranged from 3 to 67 percent of nests examined (Mayfield 1960, p. 204;
Cuthbert 1982, p. 1; Walkinshaw 1983, p. 120); however, few predation
events have been directly observed, and in general, evidence regarding
the importance of certain nest or adult predators lack quantitative
support (Mayfield 1960, p. 182; Walkinshaw 1972, p. 5; Walkinshaw 1983,
pp. 113-114).
Overall, nest predation rates for Kirtland's warblers are similar
to non-endangered passerines and are below levels that would compromise
population replacement (Bocetti 1994, pp. 125-126; Cooper et al.,
unpubl. data). The increasing numbers of house cats in the breeding and
wintering habitats is recognized (Lepczyk et al. 2003, p. 192; Horn et
al. 2011, p. 1184), but there is not sufficient evidence to conclude at
this time that predation from cats is currently having population-level
impacts to the Kirtland's warbler. Therefore, we conclude that disease
and predation do not constitute substantial threats to the Kirtland's
warbler now or in the foreseeable future.
D. Inadequacy of Existing Regulatory Mechanisms
Under this factor, we examine the threats identified within the
other factors as ameliorated or exacerbated by any existing regulatory
mechanisms or conservation efforts. Section 4(b)(1)(A) of the Act
requires that the Service 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.'' In relation to
Factor D under the Act, we interpret this language to require the
Service to consider relevant Federal, State, and Tribal laws,
regulations, and other such binding legal mechanisms that may
ameliorate or exacerbate any of the threats we describe in threat
analyses under the other four factors or otherwise enhance the species'
conservation. Our consideration of these mechanisms is described within
each of the threats to the species, where applicable (see discussion
under each of the other factors).
E. Other Natural or Manmade Factors Affecting Its Continued Existence
Brood Parasitism
Brood parasitism can depress reproduction of avian hosts in several
ways, including the direct removal or predation of eggs or young,
facilitating nest predation by other nest predators, reducing hatching
or fledging success, altering host population sex ratios, and
increasing juvenile and adult mortality beyond the nest (Elliot 1999,
p. 55; Hoover 2003, pp. 928-929; Smith et al. 2003, pp. 777-780;
Zanette et al. 2005, p. 818; Hoover and Reetz 2006, pp. 170-171; Hoover
and Robinson 2007, p. 4480; Zanette et al. 2007, p. 220). The brown-
headed cowbird is the only brood parasite within the Kirtland's
warbler's breeding range.
Although brown-headed cowbirds were historically restricted to
prairie ecosystems, forest clearing and agricultural development of
Michigan's Lower Peninsula in the late 1800s facilitated the brown-
headed cowbird's range expansion into Kirtland's warbler nesting areas
(Mayfield 1960, p. 145). Wood and Frothingham (1905, p. 49) found that
brown-headed cowbirds were already common within the Kirtland's
warbler's breeding range by the early 1900s. Strong (1919, p. 181)
later reported the first known instance of brood parasitism of a
Kirtland's warbler nest in Crawford County, Michigan, in 1908. Shortly
thereafter, Leopold (1924, p. 57) related the scarcity of Kirtland's
warblers to brown-headed cowbird parasitism. Mayfield (1960, pp. 180-
181) supported Leopold's hypothesis with empirical data, and further
recognized that brown-headed cowbird parasitism significantly affected
the survival of the Kirtland's warbler.
The Kirtland's warbler is particularly sensitive to brown-headed
cowbird brood parasitism. The warbler's limited breeding range likely
exposes the entire population to brown-headed cowbird parasitism
(Mayfield 1960, pp. 146-147; Trick, unpubl. data). In addition, the
peak egg-laying period of the brown-headed cowbird completely overlaps
with that of the Kirtland's warbler, and the majority of Kirtland's
warblers produce only one brood each year (Mayfield 1960, pp. 151-152;
Radabaugh 1972, p. 55; Rockwell, unpubl. data). Kirtland's warblers
have limited evolutionary experience with brown-headed cowbirds
compared to other hosts and have not developed effective defensive
behaviors to thwart brood parasitism (Walkinshaw 1983, pp. 157-158).
Between 1903 and 1971, researchers observed parasitism rates of
Kirtland's warbler nests ranging from 48 percent to 86 percent
(reviewed in Shake and Mattson 1975, p. 2). Brown-headed cowbirds also
appear to exert greater pressure on Kirtland's warbler nests than other
passerines within the same breeding habitat. Walkinshaw (1983, p. 154)
reported that 93 percent of all the brown-headed cowbird eggs he found
in jack pine habitat were located in Kirtland's warbler nests compared
to all other host species combined. Kirtland's warbler fledging rates
averaged less than 1 young per nest prior to the initiation of brown-
headed cowbird control (Walkinshaw 1972, p. 5).
The effect of brown-headed cowbird parasitism exacerbated negative
impacts associated with habitat loss in the decline of the Kirtland's
warbler population (Rothstein and Cook 2000, p. 7). Nicholas Cuthbert
and Bruce Radabaugh (Cuthbert 1966, pp. 1-2) demonstrated that trapping
brown-headed cowbirds within Kirtland's warbler nesting areas decreased
parasitism rates and increased Kirtland's warbler nesting success.
Accordingly, intensive brown-headed cowbird removal was recommended on
major Kirtland's warbler nesting areas as one of the necessary steps
for the recovery of the Kirtland's warbler (Shake and Mattsson 1975, p.
2).
Since 1972, the Service, in conjunction with the USDA-WS, MDNR, and
USFS, has implemented an intensive brown-headed cowbird control program
within major Kirtland's warbler nesting areas in Michigan's Lower
Peninsula. On average, the control program annually removes
approximately 3,573 brown-headed cowbirds from occupied Kirtland's
warbler habitat in northern lower Michigan (USDA-WS 2016, unpubl.
[[Page 15773]]
report). Recent trap rates, however, have been below 1,500 brown-headed
cowbirds per year (USDA-WS, unpubl. data). Brown-headed cowbird
trapping is also conducted in selected Kirtland's warbler breeding
areas in Wisconsin. The trapping program in Wisconsin started in 2008,
and is run using similar methods to the program in Michigan, with an
average of 238 brown-headed cowbirds captured per year (USDA-WS, USFWS
unpub. data).
Following the initiation of brown-headed cowbird control in
northern lower Michigan in 1972, brood parasitism rates decreased to
6.2 percent, and averaged 3.4 percent between 1972 and 1981 (Kelly and
DeCapita 1982, p. 363). Kirtland's warbler fledging rates
simultaneously increased from less than 1 per nest to 2.8 per nest, and
averaged 2.78 young fledged per nest between 1972 and 1981 (Kelly and
DeCapita 1982, pp. 364-365). Had brown-headed cowbird parasitism not
been controlled, Mayfield (1975, p. 43) calculated that by 1974, the
Kirtland's warbler population may have been reduced to only 42 pairs.
Brood parasitism of Kirtland's warbler nests also occurs in
Wisconsin. In 2007, two of three Kirtland's warbler nests were
parasitized (USFWS unpubl. data). After the initiation of brown-headed
cowbird control in 2008, brood parasitism rates in Wisconsin have
fluctuated substantially among years, from 10 percent to 66 percent
(USFWS unpubl. data; Trick unpubl. data). However, in the same time
period (2008-2017), overall nest success has ranged from 19 to 80
percent, and the average fledge rate was estimated to be between 1.51
to 1.92 chicks per nest (USFWS 2017, pp. 2-3).
Limited studies on the effectiveness of the brown-headed cowbird
control program in relation to Kirtland's warbler nest productivity in
Michigan have been conducted since the early 1980s. De Groot and Smith
(2001, p. 877) found that brown-headed cowbirds were nearly eliminated
in areas directly adjacent to a trap, and brown-headed cowbird
densities decreased 5 km (3 miles) and greater from brown-headed
cowbird removal areas. Brown-headed cowbird densities significantly
increased at distances greater than 10 km (6 miles) from brown-headed
cowbird removal areas, further demonstrating the localized effect of
brown-headed cowbird control (De Groot and Smith 2001, p. 877).
Although brown-headed cowbird density increased with distance beyond 5
km (3 miles) of brown-headed cowbird traps, brown-headed cowbird
densities were still low in those areas compared to other parts of
North America (De Groot and Smith 2001, p. 877). Anecdotal observation
of brood parasitism rates have also indicated very low levels of brood
parasitism within Kirtland's warbler nesting areas (Bocetti 1994, p.
96; Rockwell 2013, p. 93).
A study is currently underway in Michigan to evaluate the effective
range of a brown-headed cowbird trap and to determine the brood
parasitism rate of Kirtland's warbler nests when traps are not operated
during the warbler's breeding season. Beginning in 2015, 12 brown-
headed cowbird traps (out of 55 total) were closed for two breeding
seasons, and Kirtland's warbler nests were searched to determine the
rate of parasitism (Cooper et al., unpubl. data). In 2015, only one
nest out of 150 was parasitized, approximately 8 km (5 miles) away from
the nearest brown-headed cowbird trap. In 2016, similar low rates of
parasitism were observed, with only two parasitized nests out of 137.
Due to the low levels of brood parasitism observed, an additional 6
traps were closed in 2017, and none of the 100 nests observed in 2017
was parasitized (Cooper et al., unpubl. data). These preliminary data
corroborate similar findings that the effective range of a brown-headed
cowbird trap is likely much larger than the range (1.6 km (1 mile)
radius) traditionally used in planning and implementing the brown-
headed cowbird control program.
Additionally, point count surveys were conducted during 2015 and
2016, in Kirtland's warbler nesting areas in Michigan's northern Lower
Peninsula where brown-headed cowbird traps were not being operated.
Only 13 brown-headed cowbirds were observed during 271 point count
surveys (Cooper et al., unpubl. data). Trend estimate data from
Breeding Bird Survey routes between 2005 and 2015 have also shown
decreased brown-headed cowbird population trends in Michigan and the
Upper Great Lakes (Sauer et al. 2017, p. 169).
However, in similar experiments where brown-headed cowbird trapping
was reduced or brought to an end following a lengthy period of
trapping, brood parasitism rates elevated or returned to pre-trapping
rates. Research at Fort Hood Military Reservation in Texas showed that
after 3 years of decreased brown-headed cowbird trapping levels,
parasitism rates increased from 7.9 percent to 23.1 percent and
resulted in black-capped vireo (Vireo atricapilla) nest survival
decreasing to unsustainable levels (Kostecke et al. 2009, p. 1).
Kosciuch and Sandercock (2008, p. 546) found similar results with
parasitism frequency and host bird productivity returning to pre-
trapping levels quickly upon discontinuing cowbird removal.
After 45 years of brown-headed cowbird trapping in Michigan, the
threat of brood parasitism on the Kirtland's warbler has been greatly
reduced, but not eliminated. Brown-headed cowbirds are able to
parasitize more than 200 host species (Friedmann et al. 1977, p. 5),
and the effect of brown-headed cowbird parasitism is therefore not
density-dependent on any one host. Brown-headed cowbirds remain present
in jack pine habitat away from brown-headed cowbird traps, even if that
area had been trapped in previous years, but potentially in lower
numbers (DeGroot and Smith 2001, p. 877; Bailey 2007, pp. 97-98; Cooper
et al., unpubl. data). Female brown-headed cowbirds are highly
prolific, estimated to produce up to 40 eggs in a breeding season
(Scott and Ankney 1980, p. 680). Successful brown-headed cowbird
reproduction outside of trapped areas may maintain a population of
adult brown-headed cowbirds that could return in subsequent years with
the ability to parasitize Kirtland's warbler nests. It is unclear if
reduced parasitism rates are a permanent change to the landscape of
northern lower Michigan. The best available information, however,
indicates that cowbird removal efforts can be reduced without adversely
impacting Kirtland's warbler productivity rates. Given the historical
impact that the brown-headed cowbird has had on the Kirtland's warbler,
and the potential for the brown-headed cowbird to negatively affect the
warbler, a sustainable Kirtland's warbler population depends on
monitoring the magnitude and extent of brood parasitism and
subsequently adjusting the level of cowbird trapping appropriately.
The MOA (see Recovery and Recovery Plan Implementation discussion,
above) established in 2015 between the Service and MDNR addresses the
commitment and long-term costs associated with future efforts to
control cowbirds. The MOA established a dedicated account from which
income can be used to implement cowbird management and other
conservation actions for the Kirtland's warbler. To date, the account
has greater than one million dollars invested for long-term growth, and
income generated will be used to ensure sufficient cowbird management
to adequately reduce nest parasitism of the Kirtland's warbler.
Thus, we conclude that with the expected continued management, the
threat of brood parasitism by brown-headed cowbirds to the Kirtland's
[[Page 15774]]
warbler has been ameliorated to sufficiently low levels and will
continue to remain at these acceptable levels in the foreseeable
future.
Effects of Changes to Environmental Conditions
The effects of projected changes in temperature, precipitation, and
sea level on Kirtland's warblers were not identified in the listing
rule (32 FR 4001; March 11, 1967) or in the updated recovery plan
(USFWS 1985, entire), yet the potential impact of climate change has
gained widespread recognition as one of many pressures that influence
the distributions of species, the timing of biological activities and
processes, and the health of populations. Potential effects to the
Kirtland's warbler include a decrease in productivity rates, a decrease
and shift in suitable breeding habitat outside of the species' current
range (Prasad et al. 2007, unpaginated), a decrease in the extent of
wintering habitat, and decoupling the timing of migration from food
resource peaks that are driven by temperature and are necessary for
migration and feeding offspring (van Noordwijk et al. 1995, p. 456;
Visser et al. 1998, pp. 1869-1870; Thomas et al. 2001, p. 2598; Strode
2003, p. 1142).
There are a multitude of anticipated changes to the extent and
availability of suitable Kirtland's warbler habitat within jack pine
forests on the breeding grounds based on projected changes to
temperature and precipitation that range from expansion to contraction
of habitat. Continued increases in temperature and evaporation will
likely reduce jack pine forest acreage (NAST 2000, pp. 116-117), as
well as increase the susceptibility of current jack pine forests to
pests and diseases (Bentz et al. 2010, p. 609; Cudmore et al. 2010, pp.
1040-1041; Safranyik et al. 2010, p. 433). Competition with deciduous
forest species is also expected to favor an expansion of the deciduous
forest into the southern portions of the boreal forest (USFWS 2009, p.
14) and affect interspecific relationships between the Kirtland's
warbler and other wildlife (Colwell and Rangel 2009, p. 19657; Wiens et
al. 2009, p. 19729). However, warmer weather and increased levels of
carbon dioxide could also lead to an increase in tree growth rates on
marginal forestlands that are currently temperature-limited (NAST 2000,
p. 57). Additionally, higher air temperatures will cause greater
evaporation and, in turn, reduce soil moisture, resulting in conditions
conducive to forest fires (NAST 2000, p. 57) that favor jack pine
propagation. Under different greenhouse gas emission scenarios, there
may be a reduction of suitable Kirtland's warbler breeding habitat in
Michigan, as well as an expansion of suitable habitat in western
Wisconsin and Minnesota (Prasad et al. 2007, unpaginated).
On the wintering grounds, effects to the Kirtland's warbler could
occur as a result of changing temperature, precipitation, rising sea
levels, and storm events. For migratory species, unfavorable changes on
the wintering grounds can result in subsequent negative effects on
fitness later in the annual cycle (Marra et al. 1998, p. 1885; Rockwell
et al. 2012, pp. 747-748; Rockwell et al. 2017, p. 721; Sillett et al.
2000, pp. 2040-2041). For the Kirtland's warbler, wintering habitat
condition has been shown to affect survival and reproduction (Rockwell
et al. 2017, p. 721; Rockwell et al. 2012, pp. 747-748). This likely
results from limited resource availability on the wintering grounds
that reduces body condition and fat reserves necessary for successful
migration and reproduction (Wunderle et al. 2014, pp. 47-49). The
availability of sufficient food resources is affected by the extent of
habitat for arthropods and fruiting plants, temperature, and
precipitation (Brown and Sherry 2006, pp. 25-27; Wunderle et al. 2014,
p. 39).
Temperatures in the Caribbean have shown strong warming trends
across all regions, particularly since the 1970s (Jones et al. 2015,
pp. 3325, 3332), and are likely to continue to warm. Climate models
predict an increase in temperature of almost 2.5 to 3.0 degrees Celsius
(4.5-6.3 degrees Fahrenheit) above the mean temperatures of 1970-1989
by the 2080s (Karmalkar et al. 2013, p. 301). In addition to higher
mean daily temperatures, Stennett-Brown et al. (2017, pp. 4838-4840)
predict an increase in the number of warm days and nights, and a
decrease in the frequencies of cool days and nights, for 2071-2099
relative to 1961-1999. Increased temperatures could affect food
availability by altering food supply (arthropod and fruit
availability), although it is unknown to what extent the predicted
increases in temperature would increase or decrease food supply for the
Kirtland's warbler. Other effects of increasing temperature related to
sea level and precipitation are described below.
Increasing temperatures can contribute to sea level rise from the
melting of ice over land and thermal expansion of seawater. A wide
range of estimates for future global mean sea level rise are found in
the scientific literature (reviewed in Simpson et al. 2010, pp. 55-61).
The Intergovernmental Panel on Climate Change (IPCC) (2013, p. 25)
predicted a likely range in the rise in sea level of 0.26 m (0.85 ft)
to almost 1 m (3.3 ft, IPCC 2013, p. 25; Church et al. 2013, p. 1186);
other estimates in sea level rise for the same timeframe ranged from a
minimum of 0.2 m (0.7 ft) to a maximum of 2.0 m (6.6 ft) (Parris et al.
2012, p. 12). Increase in sea level could reduce the availability of
suitable habitat due to low-elevation areas being inundated, resulting
in a reduction in the size of the islands on which Kirtland's warblers
winter (Amadon 1953, p. 466; Dasgupta et al. 2009, pp. 21-23). The
Bahamas archipelago is mainly composed of small islands, and more than
80 percent of the landmass is within 1.5 m (4.9 ft) of mean sea level
(The Bahamas Environment, Science and Technology Commission 2001, p.
43). This makes The Bahamas particularly vulnerable to future rises in
sea level (Simpson et al. 2010, p. 74), which could result in reduction
of the extent of winter habitat and negatively impact the Kirtland's
warbler. Simpson et al. (2010, p. 77) estimated a loss of 5 percent of
landmass in the Bahamas due to a 1 m rise in sea level, whereas
Dasgupta et al. (2007, p. 12; 2009, p. 385) estimates 11.0 percent of
land area in The Bahamas would be impacted by a 1 m (3.3 ft) sea level
rise. Wolcott et al. (in press, unpaginated) analyzed the amount of
Kirtland's warbler habitat that would be lost due to a 1 m (3.3 ft) and
2 m (6.6 ft) rise in sea level on north and north-central islands in
The Bahamas, using high resolution land cover data for Eleuthera and
``open land'' (nonforest, urban, or water) within available GIS land
cover data for the other islands. On Eleuthera, the island with the
greatest known density of overwintering Kirtland's warblers, the amount
of available wintering habitat was reduced by 0.8 percent and 2.6
percent due to a 1 m (3.3 ft) and 2 m (6.6 ft) rise in sea level,
respectively (Wolcott et al. in press, unpaginated). Loss of habitat
was greater for northern islands of The Bahamas where elevations are
lower, and where there have historically been few observations of
Kirtland's warblers (Wolcott et al. in press, unpaginated).
Generally, climate models predict a drying trend in the Caribbean,
but there is considerable temporal and spatial variation and often
disagreement among models regarding specific predictions that make it
difficult to determine the extent to which reduced rainfall or timing
of rainfall may affect the Kirtland's warbler in the future. We
reviewed available literature examining precipitation trends and
projections in the Caribbean, and specifically The
[[Page 15775]]
Bahamas, to assess the potential effects of changes in precipitation.
Jones et al. (2016, p. 10) found that precipitation trends in the
Caribbean from 1979-2012 did not show statistically significant
century-scale trends across regions, but there were periods of up to 10
years when some regions were drier or wetter than the long-term
averages. In the northern Caribbean (which includes The Bahamas, Cuba,
Jamaica, Haiti, Dominican Republic, and Puerto Rico), some years were
more wet than the average, and other years were more dry across all
seasons (Jones et al. 2016, p. 3314), with higher precipitation totals
since about 2000. Within The Bahamas, precipitation trends during the
dry season (November through April) showed a significant drying trend
for 1979-2009 (Jones et al. 2016, pp. 3328, 3331).
Karmalkar et al. (2013, entire) used available climate model data
to provide both present-day and scenario-based future predictions on
precipitation and temperature for the Caribbean islands. Projected
trends in The Bahamas by the 2080s show relatively small changes in
terms of wet season precipitation, with a small decrease in
precipitation in the early part of the wet season (May through July)
and a slight increase in the late wet season (August through October)
in the northern parts of The Bahamas (Karmalkar et al. 2013, p. 297).
In one model, the dry season was predicted to remain largely the same,
except for a small increase in precipitation in November, whereas an
alternate model projected The Bahamas would experience wetter
conditions in the dry season, including during March (Karmalkar et al.
2013, pp. 298, 299).
Finally, Wolcott et al. (in press, unpaginated) modeled projected
changes in precipitation under two scenarios with varying future carbon
dioxide (CO2) emissions and found that the projected
precipitation varied seasonally and spatially throughout the islands of
The Bahamas, both in the mid-term (2050) and long-term (2100). The
northern and north-central islands are likely to have increased
precipitation in March (compared to baseline conditions), whereas the
central islands are likely to become drier.
Accurately projecting future precipitation trends in the Caribbean
is difficult due to the complex interactions between sea surface
temperatures, atmospheric pressure at sea level, and predominant wind
patterns. Further, some models have difficulty accurately simulating
the semi-annual seasonal cycle of precipitation observed in the
Caribbean. Recent models using statistical downscaling techniques have
improved resolution, but still show limitations for predicting
precipitation. Thus, rainfall projections where Kirtland's warblers
overwinter have limited certainty and should be interpreted with
caution. Understanding the likely projected precipitation in the
Bahamas and Caribbean is important because of the strong link between
late winter rainfall and fitness of Kirtland's warblers. A drying trend
on the wintering grounds will likely cause a corresponding reduction in
available food resources (Studds and Marra 2007, pp. 120-121; Studds
and Marra 2011, pp. 4-6). Rainfall in the previous month was an
important factor in predicting fruit abundance (both ripe and unripe
fruit) for wild sage and black torch in The Bahamas (Wunderle et al.
2014, p. 19), which is not surprising given the high water content (60-
70 percent) of their fruit (Wunderle unpubl. data, cited in Wunderle et
al. 2014, p. 4). Carry-over effects of weather on the wintering
grounds, particularly late-winter rainfall, have been shown to affect
spring arrival dates, reproductive success, and survival rates of
Kirtland's warblers (reviewed in Wunderle and Arendt 2017, pp. 5-12;
Rockwell et al. 2012, p. 749; Rockwell et al. 2017, pp. 721-722).
Decreases in rainfall and resulting decreases in food availability
may also result in poorer body condition prior to migration. The need
to build up the necessary resources to successfully complete migration
could, in turn, result in delays to spring departure in dry years
(Wunderle et al. 2014, p. 16) and may explain observed delays in
arrival times following years with less March rainfall in The Bahamas
(Rockwell et al. 2012, p. 747). Delays in the spring migration of
closely related American redstarts (Setophaga ruticilla) have also been
directly linked to variation in March rainfall and arthropod biomass
(Studds and Marra 2007, p. 120; Studds and Marra 2011, p. 4) and have
also resulted in fewer offspring produced per summer (Reudinck et al.
2009, p. 1624). These results strongly indicate that environmental
conditions modify the phenology of spring migration, which likely
carries a reproductive cost. If The Bahamas experience a significant
winter drying trend, Kirtland's warblers may be pressured to delay
spring departures, while simultaneously contending with warming trends
in their breeding range that pressure them to arrive earlier in the
spring. Projection population modeling (Rockwell et al. 2017, p. 2)
estimated a negative population growth in Kirtland's warbler as a
result of a reduction (by more than 12.4 percent from the current mean
levels) in March rainfall.
Extreme weather events such as tropical storms and hurricanes will
continue to occur with an expected reduction in the overall frequency
of weaker tropical storms and hurricanes, but an increase in the
frequency of the most intense hurricanes (category 4 and 5 hurricanes),
based on several dynamical climate modeling studies of Atlantic basin
storm frequency and intensity (Bender et al. 2010, p. 456; Knutson et
al. 2010, pp. 159-161; Murakami et al. 2012a, pp. 2574-2576; Murakami
et al. 2012b, pp. 3247-3253; Knutson et al. 2013, pp. 6599-6613;
Knutson et al. 2015, pp. 7213-7220). Although very intense hurricanes
are relatively rare, they inflict a disproportionate impact in terms of
storm damage (e.g., approximately 93 percent of damage resulting from
hurricanes is caused by only 10 percent of the storms Mendelsohn et al.
2012, p. 3). Hurricanes have the potential to result in direct
mortality of Kirtland's warblers during migration and while on the
wintering grounds (Mayfield 1992, p. 11), but the more significant
effects generally occur following the hurricane due to altered shelter
and food (Wiley and Wunderle 1993, pp. 331-336). Because Kirtland's
warblers readily shift sites on the wintering grounds based on food
availability, Kirtland's warblers would likely be able to shift
locations within and possibly between nearby islands as an immediate
post-hurricane response (Wunderle et al. 2007, p. 124). Further,
hurricanes likely produce new wintering habitat for Kirtland's warblers
by opening up closed canopy habitat of tall coppice, and may also help
set back succession for existing suitable habitat (Wunderle et al.
2007, p. 126).
Because of the uncertainties in modeling the projected changes in
precipitation, both spatially and temporally, there is a great level of
uncertainty in how precipitation is likely to change in the foreseeable
future and thereby affect Kirtland's warbler. There is more confidence
that temperatures are likely to increase, and it is possible that there
will be a drying trend over much of the Caribbean. However, it is not
clear whether all islands will be equally affected by less
precipitation. As a long-distance migrant, the Kirtland's warbler is
well suited, in terms of its movement patterns and dispersal ability,
to reach other locations outside of their current winter range where
suitable winter habitat and food resources may be more
[[Page 15776]]
available under future temperature and precipitation conditions.
Individuals have been reported wintering outside of The Bahamas (see
Distribution discussion above), though the extent of behavioral
plasticity and adaptive capacity at the species level to shift
locations in response to future, long-term precipitation and
temperature conditions in the Caribbean remains unknown.
Collision With Lighted and Human-Made Structures
Collision with human-made structures (e.g., tall buildings,
communication towers, wind turbines, power lines, heavily lighted
ships) kills or injures millions of migrating songbirds annually
(reviewed in Drewitt and Langston 2008, p. 259; Longcore et al. 2008,
pp. 486-489). Factors that influence the likelihood of avian collisions
with human-made structures include size, location, the use of lighting,
and weather conditions during migratory periods (reviewed in Drewitt
and Langston 2008, p. 233). The presence of artificial light at night
and plate-glass windows are the most important factors influencing
avian collisions with existing human-made structures (Ogden 1996, p.
4).
There are five confirmed reports of Kirtland's warblers colliding
with human-made structures, all of which resulted in death. Two of
these deaths resulted from collisions with windows (Kleen 1976, p. 78;
Kramer 2009, pers. comm.), and three resulted from collisions with a
lighted structure, including a lighthouse (Merriam 1885, p. 376), an
electric light mast (Jones 1906, pp. 118-119), and a lighted monument
(Nolan 1954). Another report of a Kirtland's warbler that flew into a
window and appeared to survive after only being stunned by the
collision (Cordle 2005, p. 2) was not accepted as an official
documented observation of a Kirtland's warbler (Maryland Ornithological
Society 2010, unpaginated).
Some bird species may be more vulnerable to collision with human-
made structures than others due to species-specific behaviors.
Particularly vulnerable species include: Night-migrating birds that are
prone to capture or disorientation by artificial lights because of the
way exposure to a light field can disrupt avian navigation systems;
species that habitually make swift flights through restricted openings
in dense vegetation; and species that are primarily active on or near
the ground (reviewed in Ogden 1996, p. 8; Gauthreaux and Belser 2006,
p. 67). Of the avian species recorded, the largest proportion of
species (41 percent) that suffer migration mortality at human-made
structures belong to the wood warbler subfamily (Parulinae), of which
many species exhibit the above-mentioned behaviors (Ogden 1996, p. 14).
The Kirtland's warbler belongs to the Parulinae subfamily and
exhibits many of the behaviors characteristic of other birds considered
vulnerable to collision with human-made structures, yet little is known
regarding how prone this species is to collision. The majority of bird
collisions go undetected because corpses land in inconspicuous places
or are quickly removed by scavengers postmortem (Klem 2009, p. 317).
Additionally, while most avian collisions take place during migration,
detailed information about Kirtland's warbler migration is still
limited. The Kirtland's warbler population is also small, reducing the
probability of collision observations by chance alone, compared to
other species. These factors have inhibited the gathering of
information, and in turn, a more comprehensive understanding of the
hazards human-made structures pose to the Kirtland's warbler. It is
reasonable to presume, however, that more Kirtland's warblers collide
with human-made structures than are reported.
Solutions to reduce the hazards that cause avian collisions with
human-made structures are being implemented in many places.
Extinguishing internal lights of buildings at night, avoiding the use
of external floodlighting, and shielding the upward radiation of low-
level lighting such as street lamps are expected to reduce attraction
and trapping of birds within illuminated urban areas, and in turn,
injury and mortality caused by collision, predation, starvation, or
exhaustion (reviewed in Ogden 1996, p. 31). The Service's Urban
Conservation Treaty for Migratory Birds program has worked with several
cities to adopt projects that benefit migrating birds flying through
urban areas in between breeding and wintering grounds. For example,
some cities within the Kirtland's warbler's migration corridor, such as
Chicago, Indianapolis, Columbus, Detroit, and Milwaukee, have ``Lights
Out'' or similar programs, which encourage the owners and managers of
tall buildings to turn off or dim exterior decorative lights as well as
interior lights during spring and fall migration periods (http://www.audubon.org/conservation/existing-lights-out-programs). These
programs are estimated to reduce general bird mortality by up to 83
percent (Field Museum 2007, p. 1).
Additionally, migrating birds are not equally attracted to various
lighting patterns, and modifying certain types of lighting systems
could significantly reduce collision-related mortality. Gehring et al.
(2009, p. 509) reported that by removing steady-burning, red L-810
lights and using only flashing, red L-864 or white L-865 lights on
communication towers and other similarly lit aeronautical obstructions,
mortality rates could be reduced by as much as 50 to 70 percent. On
December 4, 2015, the Federal Aviation Administration revised its
advisory circular that prescribes tower lighting to eliminate the use
of L-810 steady-burning side lights on towers taller than 107 m (350
ft) (AC 70/7460-1L), and on September 28, 2016, released specifications
for flashing L-810 lights on towers 46-107 m (150-350 ft) tall. These
lighting changes should significantly reduce the risk of migratory bird
collisions with communication towers.
As noted previously concerning potential threats to migratory
habitat, if mortality during migration were limiting or likely to limit
the population to the degree that maintaining a healthy population may
be at risk, it should be apparent in the absence of the species from
highly suitable breeding habitat in the core breeding range. In fact,
we have seen just the opposite, increasing densities of breeding
individuals in core areas and a range expansion into what would appear
to be less suitable habitat elsewhere. This steady population growth
and range expansion occurred while the potential threats to the species
during migration were all increasing on the landscape (e.g., new
communication towers and wind turbines); therefore, we conclude that
collision with lighted and human-made structures does not constitute a
substantial threat to the Kirtland's warbler now or in the foreseeable
future.
Synergistic Effects of Factors A Through E
When threats occur together, one may exacerbate the effects of
another, causing effects not accounted for when threats are analyzed
individually. Many of the threats to the Kirtland's warbler and its
habitat discussed above under Factors A through E are interrelated and
could be synergistic, and thus may cumulatively impact Kirtland's
warbler beyond the extent of each individual threat. For example,
increases in temperature and evaporation could reduce the amount of
jack pine habitat available and increase the level of brood parasitism.
Historically, habitat loss and brood parasitism significantly impacted
[[Page 15777]]
the Kirtland's warbler and cumulatively acted to reduce its range and
abundance. Today, these threats have been ameliorated and adequately
minimized such that the species has exceeded the recovery goal. The
best available data show a positive population trend over several
decades and record high population levels. At a high enough population
level, the Kirtland's warbler can withstand certain threats and
continue to be resilient. Continued habitat management and brown-headed
cowbird control at sufficient levels, as identified in the Conservation
Plan and at levels consistent with those to which management agencies
committed in the MOU and MOA, will assure continued population numbers
at or above the recovery criteria with the current magnitude of other
threats acting on the Kirtland's warbler.
Proposed Determination of Species Status
Section 4 of the Act (16 U.S.C. 1533), and its implementing
regulations at 50 CFR part 424, set forth the procedures for
determining whether a species is an endangered species or threatened
species and should be included on the Federal Lists of Endangered and
Threatened Wildlife and Plants. 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 throughout all or a
significant portion of its range within the foreseeable future.''
On July 1, 2014, we published a final policy interpreting the
phrase ``significant portion of its range'' (SPR) (79 FR 37578).
Aspects of that policy were vacated for species that occur in Arizona
by the U.S. District Court for the District of Arizona (CBD v. Jewell,
No. CV-14-02506-TUC-RM (March 29, 2017), clarified by the court, March
29, 2017). Since the Kirtland's warbler does not occur in Arizona, for
this finding we rely on the SPR policy, and also provide additional
explanation and support for our interpretation of the SPR phrase. In
our policy, we interpret the phrase ``significant portion of its
range'' in the Act's definitions of ``endangered species'' and
``threatened species'' to provide an independent basis for listing a
species in its entirety; thus there are two situations (or factual
bases) under which a species would qualify for listing: A species may
be in danger of extinction or likely to become so in the foreseeable
future throughout all of its range; or a species may be in danger of
extinction or likely to become so throughout a significant portion of
its range. If a species is in danger of extinction throughout an SPR,
it, the species, is an ``endangered species.'' The same analysis
applies to ``threatened species.''
Our final policy addresses the consequences of finding a species is
in danger of extinction in an SPR, and what would constitute an SPR.
The final policy states that (1) if a species is found to be endangered
or threatened throughout a significant portion of its range, the entire
species is listed as an endangered species or a threatened species,
respectively, and the Act's protections apply to all individuals of the
species wherever found; (2) a portion of the range of a species is
``significant'' if the species is not currently endangered or
threatened throughout all of its range, but the portion's contribution
to the viability of the species is so important that, without the
members in that portion, the species would be in danger of extinction,
or likely to become so in the foreseeable future, throughout all of its
range; (3) the range of a species is considered to be the general
geographical area within which that species can be found at the time
the Service or the National Marine Fisheries Service makes any
particular status determination; and (4) if a vertebrate species is
endangered or threatened throughout an SPR, and the population in that
significant portion is a valid DPS, we will list the DPS rather than
the entire taxonomic species or subspecies.
The SPR policy applies to analyses for all status determinations,
including listing, delisting, and reclassification determinations. The
procedure for analyzing whether any portion is an SPR is similar,
regardless of the type of status determination we are making. The first
step in our assessment of the status of a species is to determine its
status throughout all of its range. We subsequently examine whether, in
light of the species' status throughout all of its range, it is
necessary to determine its status throughout a significant portion of
its range. If we determine that the species is in danger of extinction,
or likely to become so in the foreseeable future, throughout all of its
range, we list the species as an endangered (or threatened) species and
no SPR analysis will be required. As described in our policy, once the
Service determines that a ``species''--which can include a species,
subspecies, or distinct population segment (DPS)--meets the definition
of ``endangered species'' or ``threatened species,'' the species must
be listed in its entirety and the Act's protections applied
consistently to all individuals of the species wherever found (subject
to modification of protections through special rules under sections
4(d) and 10(j) of the Act).
Under section 4(a)(1) of the Act, we determine whether a species is
an endangered species or threatened species because of any of the
following 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. These same factors apply whether we
are analyzing the species' status throughout all of its range or
throughout a significant portion of its range.
Determination of Status Throughout All of the Kirtland's Warbler's
Range
We conducted a review of the status of the Kirtland's warbler and
assessed the five factors to evaluate whether the species is in danger
of extinction, or likely to become so in the foreseeable future,
throughout all of its range. The size of the Kirtland's warbler
population is currently at its known historical maximum, which is
nearly 10 times larger than it was at the time of listing and close to
2.5 times larger than the recovery goal. The population's breeding
range also expanded outside of the northern Lower Peninsula to areas in
Michigan's Upper Peninsula, Wisconsin, and Ontario. This recovery is
attributable to successful interagency cooperation in the management of
habitat and brood parasitism. The amount of suitable habitat has
increased by approximately 150 percent since listing, primarily due to
the increased amount of planted habitat generated from adaptive
silvicultural techniques. Brown-headed cowbird control has been
conducted on an annual basis within the majority of Kirtland's warbler
nesting areas since 1972, and has greatly reduced the impacts of brood
parasitism.
During our analysis, we found that impacts believed to be threats
at the time of listing have been eliminated or reduced, or are being
adequately managed since listing, and we do not expect any of these
conditions to substantially change after delisting and into the
foreseeable future. Population modeling that assessed the long-term
population viability of Kirtland's warbler populations showed stable
populations over a 50-year simulation period with current habitat
management and maintaining sufficient cowbird
[[Page 15778]]
removal (see Population Viability discussion, above). Brood parasitism
and availability of sufficient suitable breeding habitat are adequately
managed through the Kirtland's Warbler Breeding Range Conservation Plan
and the 2016 MOU. The Conservation Plan and the MOU acknowledge the
conservation-reliant nature of the Kirtland's warbler and the need for
continued habitat management and brown-headed cowbird control, and
affirm that the necessary long-term management actions will continue.
The species is resilient to threats including changing weather patterns
and sea level rise due to climate change, collision with lighted and
human-made structures, impacts to wintering and migratory habitat, and
cumulative effects, and existing information indicates that this
resilience will not change in the foreseeable future. These conclusions
are supported by the available information regarding species abundance,
distribution, and trends. Thus, after assessing the best available
information, we conclude that the Kirtland's warbler is not in danger
of extinction throughout all of its range, nor is it likely to become
so within the foreseeable future.
Determination of Status Throughout a Significant Portion of the
Kirtland's Warbler's Range
Consistent with our interpretation that there are two independent
bases for listing species, as described above, after examining the
status of the Kirtland's warbler throughout all of its range, we now
examine whether it is necessary to determine its status throughout a
significant portion of its range. Per our final SPR policy, we must
give operational effect to both the ``throughout all'' of its range
language and the SPR phrase in the definitions of ``endangered
species'' and ``threatened species.'' As discussed earlier and in
greater detail in the SPR policy, we have concluded that to give
operational effect to both the ``throughout all'' language and the SPR
phrase, the Service should conduct an SPR analysis if (and only if) a
species does not warrant listing according to the ``throughout all''
language.
Because we determined that the Kirtland's warbler is not in danger
of extinction or likely to become so within the foreseeable future
throughout all of its range, we will consider whether there are any
significant portions of its range in which the species is in danger of
extinction or likely to become so. To undertake this analysis, we first
identify any portions of the species' range that warrant further
consideration. The range of a species can theoretically be divided into
portions in an infinite number of ways. However, there is no purpose in
analyzing portions of the range that have no reasonable potential to be
significant or in analyzing portions of the range in which there is no
reasonable potential for the species to be in danger of extinction or
likely to become so in the foreseeable future in that portion. To
identify only those portions that warrant further consideration, we
determine whether there are any portions of the species' range: (1)
That may be ``significant,'' and (2) where the species may be in danger
of extinction or likely to become so within the foreseeable future. We
emphasize that answering these questions in the affirmative is not
equivalent to a determination that the species should be listed--
rather, it is a step in determining whether a more-detailed analysis of
the issue is required.
If we identify any portions (1) that may be significant and (2)
where the species may be in danger of extinction or likely to become so
within the foreseeable future, we conduct a more thorough analysis to
determine whether both of these standards are indeed met. The
determination that a portion that we have identified does meet our
definition of significant does not create a presumption, prejudgment,
or other determination as to whether the species is in danger of
extinction or likely to become so within the foreseeable future in that
identified SPR. We must then analyze whether the species is in danger
of extinction or likely to become so within the SPR. To make that
determination, we use the same standards and methodology that we use to
determine if a species is in danger of extinction or likely to become
so within the foreseeable future throughout all of its range (but
applied only to the portion of the range now being analyzed).
In practice, one key part of identifying portions appropriate for
further analysis may be whether the threats are geographically
concentrated. If a species is not in danger of extinction or likely to
become so within the foreseeable future throughout all of its range and
the threats to the species are essentially uniform throughout its
range, then there is no basis on which to conclude that the species may
be in danger of extinction or likely to become so within the
foreseeable future in any portion of its range. Therefore, we examined
whether any threats are geographically concentrated in some way that
would indicate the species may be in danger of extinction, or likely to
become so, in a particular area. Kirtland's warblers occupy different
geographic areas throughout their annual life cycle (breeding grounds,
migratory routes, wintering grounds). Although there are different
threats during time spent in each of these areas, the entire population
moves through the full annual cycle (breeding, migration, and
wintering) and functions as a single panmictic population (see Genetics
discussion above). Because all individuals move throughout all of these
geographic areas, these different geographic areas do not represent
biologically separate populations that could be exposed to different
threats. The entire population and all individuals move through each of
these geographic areas and are exposed to the same threats as they do;
thus, no portion could have a different status.
Although there are different threats acting on the species on the
breeding grounds, migratory routes, and wintering grounds (see
discussion under Factors A through E, above), the entire Kirtland's
warbler population experiences all of these threats at some point
during their annual cycle and those threats, in combination, have an
overall low-level effect on the species as a whole. Threats throughout
the species' range are being managed or are occurring at low levels, as
is evident in the species' continued population growth over the last
two decades. Commitments by management agencies through the MOA and MOU
provide assurances that habitat management and brown-headed cowbird
control will continue at sufficient levels to ensure continued stable
population numbers. We conclude that there are no portions of the
species' range that are likely to be both significant and be in danger
of extinction or likely to become so in the foreseeable future.
Therefore, no portion warrants further consideration to determine
whether the species is in danger of extinction or likely to become so
in a significant portion of its range. For these reasons, we conclude
that the species is not in danger of extinction, or likely to become so
within the foreseeable future, throughout a significant portion of its
range.
Conclusion
We have carefully assessed the best scientific and commercial
information available regarding the past, present, and future threats
to the Kirtland's warbler. The threats that led to the species being
listed under the Act (primarily loss of the species' habitat (Factor A)
and effects of brood parasitism by brown-headed cowbirds (Factor E))
have been removed, ameliorated, or are being appropriately
[[Page 15779]]
managed by the actions of multiple conservation partners over the past
50 years. These actions include habitat management, brown-headed
cowbird control, monitoring, research, and education. Given commitments
shown by the cooperating agencies entering into the Kirtland's warbler
MOU and the long record of engagement and proactive conservation
actions implemented by the cooperating agencies over a 50-year period,
we expect conservation efforts will continue to support a healthy,
viable population of the Kirtland's warbler post-delisting and into the
foreseeable future. Furthermore, there is no information to conclude
that at any time over the next 50-year window (as we define the
foreseeable future for this species) that the species will be in danger
of extinction. Thus, we have determined that none of the existing or
potential threats, either alone or in combination with others, are
likely to cause the Kirtland's warbler to be in danger of extinction
throughout all or a significant portion of its range, nor are they
likely to cause the species to become endangered within the foreseeable
future throughout all or a significant portion of its range. On the
basis of our evaluation, we conclude that, due to recovery, the
Kirtlands warbler is not an endangered or threatened species. We
therefore propose to remove the Kirtland's warbler from the Federal
List of Endangered and Threatened Wildlife at 50 CFR 17.11(h) due to
recovery.
Effects of This Rule
This proposal, if made final, would revise 50 CFR 17.11(h) by
removing the Kirtland's warbler from the Federal List of Endangered and
Threatened Wildlife. The prohibitions and conservation measures
provided by the Act, particularly through sections 7 and 9, would no
longer apply to this species. Federal agencies would no longer be
required to consult with the Service under section 7 of the Act in the
event that activities they authorize, fund, or carry out may affect the
Kirtland's warbler. There is no critical habitat designated for this
species. Removal of the Kirtland's warbler from the List of Endangered
and Threatened Wildlife would not affect the protection given to all
migratory bird species under the MBTA.
Post-Delisting Monitoring
Section 4(g)(1) of the Act requires us, in cooperation with the
States, to implement a system to monitor for not less than 5 years for
all species that have been recovered and delisted. The purpose of this
requirement is to develop a program that detects the failure of any
delisted species to sustain itself without the protective measures
provided by the Act. If, at any time during the monitoring period, data
indicate that protective status under the Act should be reinstated, we
can initiate listing procedures, including, if appropriate, emergency
listing.
We will coordinate with other Federal agencies, State resource
agencies, interested scientific organizations, and others as
appropriate to develop and implement an effective post-delisting
monitoring (PDM) plan for the Kirtland's warbler. The PDM plan will
build upon current research and effective management practices that
have improved the status of the species since listing. Ensuring
continued implementation of proven management strategies, such as
brown-headed cowbird control and habitat management, that have been
developed to sustain the species will be a fundamental goal for the PDM
plan. The PDM plan will identify measurable management thresholds and
responses for detecting and reacting to significant changes in the
Kirtland's warbler's numbers, distribution, and persistence. If
declines are detected equaling or exceeding these thresholds, the
Service, in combination with other PDM participants, will investigate
causes of these declines. The investigation will be to determine if the
Kirtland's warbler warrants expanded monitoring, additional research,
additional habitat protection or brood parasite management, or
resumption of Federal protection under the Act.
Required Determinations
Clarity of This Proposed Rule
We are required by Executive Orders 12866 and 12988 and by the
Presidential Memorandum of June 1, 1998, to write all rules in plain
language. This means that each rule we publish must:
(a) Be logically organized;
(b) Use the active voice to address readers directly;
(c) Use clear language rather than jargon;
(d) Be divided into short sections and sentences; and
(e) Use lists and tables wherever possible.
If you feel that we have not met these requirements, send us
comments by one of the methods listed in ADDRESSES. To better help us
revise the rule, your comments should be as specific as possible. For
example, you should tell us the numbers of the sections or paragraphs
that are unclearly written, which sections or sentences are too long,
the sections where you feel lists or tables would be useful, etc.
National Environmental Policy Act
We determined that we do not need to prepare an environmental
assessment or an environmental impact statement, as defined under the
authority of the National Environmental Policy Act of 1969 (42 U.S.C.
4321 et seq.), in connection with regulations adopted 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).
Government-to-Government Relationship With Tribes
In accordance with the President's memorandum of April 29, 1994,
``Government-to-Government Relations with Native American Tribal
Governments'' (59 FR 22951), Executive Order 13175, Secretarial Order
3206, the Department of the Interior's manual at 512 DM 2, and the
Native American Policy of the Service, January 20, 2016, we readily
acknowledge our responsibility to communicate meaningfully with
recognized Federal Tribes on a government-to-government basis. We will
coordinate with tribes in the Midwest within the range of the
Kirtland's warbler and request their input on this proposed rule.
References Cited
A complete list of all references cited in this proposed rule is
available at http://www.regulations.gov under Docket No. FWS-R3-ES-
2018-0005 or upon request from the Field Supervisor, Michigan
Ecological Services Field Office (see FOR FURTHER INFORMATION CONTACT).
Authors
The primary authors of this proposed rule are staff members of the
Michigan Ecological Services Field Office in East Lansing, Michigan, in
coordination with the Midwest Regional Office in Bloomington,
Minnesota.
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 set forth below:
[[Page 15780]]
PART 17--ENDANGERED AND THREATENED WILDLIFE AND PLANTS
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.
Sec. [thinsp]17.11 [Amended]
0
2. Amend Sec. [thinsp]17.11(h) by removing the entry ``Warbler (wood),
Kirtland's'' under ``BIRDS'' from the List of Endangered and Threatened
Wildlife.
Dated: March 8, 2018.
James W. Kurth,
Deputy Director, U.S. Fish and Wildlife Service, Exercising the
Authority of the Director, U.S. Fish and Wildlife Service.
[FR Doc. 2018-06864 Filed 4-11-18; 8:45 am]
BILLING CODE 4333-15-P