[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]



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 

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.


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 
    (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 

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 
    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


    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).


    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).


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).
    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 

[[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).
    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. 
    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. 

    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 
    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 
    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 
    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 
    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 
    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 
    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. 
    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 
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. 
    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 

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 

    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 
    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'' 
    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 


    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 

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 
    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).


    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, 

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]]


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]

2. Amend Sec.  [thinsp]17.11(h) by removing the entry ``Warbler (wood), 
Kirtland's'' under ``BIRDS'' from the List of Endangered and Threatened 

    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]