# Endangered and Threatened Wildlife and Plants; Final Rule Determining Endangered Status for the Southwestern Willow Flycatcher

> Briefs, arguments, decisions, and more.

URL: https://www.frixlaw.com/law-library/documents/fr%3A95-4531

## Record

- **Collection:** Federal Register
- **Document type:** Rule
- **Published:** February 27, 1995
- **Citation:** 60 FR 10694

## Text

SUMMARY: The Fish and Wildlife Service (Service) determines the
southwestern willow flycatcher (Empidonax traillii extimus) to be an
endangered species under the authority of the Endangered Species Act of
1973, as amended (Act). The breeding range of this bird includes
southern California, southern Nevada, southern Utah, Arizona, New
Mexico, western Texas, southwestern Colorado, and extreme northwestern
Mexico. Within this region, the species is restricted to dense riparian
associations of willow, cottonwood, buttonbush, and other deciduous
shrubs and trees. This habitat was historically rare and sparsely
distributed and is currently more rare owing to extensive destruction
and modification. The southwestern willow flycatcher is endangered by
extensive loss of habitat, brood parasitism, and lack of adequate
protective regulations. This rule implements Federal protection
provided by the Act for the southwestern willow flycatcher. Designation
of critical habitat for the southwestern willow flycatcher is deferred
while the Service gathers further comments and reconsiders the prudence
of designation and the appropriate boundaries of any area to be
designated.

DATES: The listing of the southwestern willow flycatcher is effective
March 29, 1995. Comments on the designation of critical habitat may be
submitted until April 28, 1995.

ADDRESSES: The complete file for this rule is available for inspection,
by appointment, during normal business hours at Ecological Services
State Office, U.S. Fish and Wildlife Service, 2321 West Royal Palm
Road, Suite 103, Phoenix, Arizona 85021.

FOR FURTHER INFORMATION CONTACT: Sam F. Spiller or Robert M. Marshall
at the above address (Telephone 602/640-2720).
SUPPLEMENTARY INFORMATION:

Background

The southwestern willow flycatcher is a small bird, approximately
15 centimeters (cm) (5.75 inches) long. It has a grayish-green back and
wings, whitish throat, light grey-olive breast, and pale yellowish
belly. Two wingbars are visible; the eye ring is faint or absent. The
upper mandible is dark, the lower is light. The song is a sneezy
``fitz-bew'' or ``fit-za-bew,'' the call a repeated ``whitt.''
The southwestern willow flycatcher occurs in riparian habitats
along rivers, streams, or other wetlands, where dense growths of
willows (Salix sp.), Baccharis, arrowweed (Pluchea sp.), buttonbush
(Cephalanthus sp.), tamarisk (Tamarix sp.), Russian olive (Eleagnus
sp.) or other plants are present, often with a scattered overstory of
cottonwood (Populus sp.) (Grinnell and Miller 1944, Phillips 1948,
Phillips et al. 1964, Whitmore 1977, Hubbard 1987, Unitt 1987,
Whitfield 1990, Brown and Trosset 1989, Brown 1991, Sogge et al. 1993,
Muiznieks et al. 1994). Throughout the range of E. t. extimus, these
riparian habitats tend to be rare, widely separated, small and/or
linear locales, separated by vast expanses of arid lands. The
southwestern willow flycatcher has experienced extensive loss and
modification of this habitat and is also endangered by other factors,
including brood parasitism by the brown-headed cowbird (Molothrus ater)
(Unitt 1987, Ehrlich et al. 1992, Sogge et al. 1993, Muiznieks et al.
1994).
The southwestern willow flycatcher (Order Passeriformes; Family
Tyrannidae) is a subspecies of one of the ten North American
flycatchers in the genus Empidonax. The willow flycatcher and alder
flycatcher (E. alnorum) were once considered a single species, the
Traill's flycatcher (E. traillii). Some sources [American
Ornithologists' Union (AOU) 1983, McCabe 1991] treat E. traillii and E.
alnorum, and all their subspecies as a superspecies, the ``traillii
complex''. However, the two species are distinguishable by morphology
(Aldrich 1951), song type, habitat use, structure and placement of
nests (Aldrich 1953), eggs (Walkinshaw 1966), ecological separation
(Barlow and McGillivray 1983), and genetic distinctness (Seutin and
Simon 1988). The breeding range of the alder flycatcher generally
occurs north of the willow flycatcher's range.
The southwestern willow flycatcher is one of five subspecies of the
willow flycatcher currently recognized (Hubbard 1987, Unitt 1987,
Browning 1993) (Figure 1.). The breeding ranges of the widely
distributed E. t. traillii and E. t. campestris extend across the
northern United States and southern Canada, from New England and Nova
Scotia west, through northern Wyoming and Montana, and into British
Columbia. Hubbard (1987) and Unitt (1987) treated E. t. campestris as
synonymous with E. t. traillii, but Browning (1993) considered them
separate subspecies (Figure 1.). The subspecies E. t. adastus breeds
from Colorado west of the plains, west through the Great Basin States
and into the eastern portions of California, Oregon and Washington. The
breeding range of E. t. brewsteri extends from the central California
coast north, through western Oregon and Washington to Vancouver Island.
The breeding range of the southwestern willow flycatcher (E. t.
extimus) includes southern California, southern Nevada, southern Utah,
Arizona, New Mexico, and western Texas (Hubbard 1987, Unitt 1987,
Browning 1993). It may also breed in southwestern Colorado, but nesting
records are lacking. Records of probable breeding E. t. extimus in
Mexico are few and are restricted to extreme northern Baja California
del Norte and Sonora (Unitt 1987, Wilbur 1987).
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The willow flycatcher subspecies are distinguished primarily by
subtle differences in color and morphology. Unitt (1987) noted that
these differences ``* * * are minor, but differ little in magnitude
from those distinguishing the species E. traillii from E. alnorum. In
Empidonax, small differences in morphology may mask large differences
in biology.''
The subspecies E. t. extimus was described by A.R. Phillips (1948)
from a collection by G. Monson from the lower San Pedro River in
southeastern Arizona. The taxonomy of E. t. extimus was critically
reviewed by Hubbard (1987), Unitt (1987), and Browning (1993). Hubbard
(1987) gave a qualified endorsement of the validity of E. t. extimus,
recommending continued examination of the taxonomy. Unitt (1987) found
that E. t. extimus was distinguishable from other willow flycatchers by
color, being paler, and morphology (primarily wing formula) but not
overall size. Browning (1993) also found that E. t. extimus was
distinguishable as a more pale-colored subspecies. The song dialect of
E. t. extimus may also be distinguishable from other willow
flycatchers. Rather than the crisp, sneezy ``fitz-bew'' of the
northerly subspecies, E. t. extimus sings a more protracted, slurred
``fit-za-bew,'' with a burry ``bew'' syllable (recordings by M. Sogge
and J. Travis). The subspecies E. t. extimus is accepted by most
authors (e.g., Aldrich 1951, Behle and Higgins 1959, Phillips et al.
1964, Bailey and Niedrach 1965, Oberholser 1974, Monson and Phillips
1981, Harris et al. 1987, Schlorff 1990, Harris 1991). Section 3(15) of
the Act and regulations at 50 CFR 424.02(k) defines the term
``species'' as any subspecies of fish or wildlife or plants, and any
distinct population segment of any vertebrate species which interbreeds
when mature. Based on the above information, the Service has determined
that E. t. extimus is eligible for protection under the Act.
The southwestern willow flycatcher nests in thickets of trees and
shrubs approximately 4-7 meters (m) (13-23 feet) or more in height,
with dense foliage from approximately 0-4 m (13 feet) above ground, and
often a high canopy cover percentage. The diversity of nest site plant
species may be low (e.g., willows) or comparatively high (e.g.,
mixtures of willow, buttonbush, cottonwood, boxelder, Russian olive,
Baccharis, and tamarisk). Nest site vegetation may be even- or uneven-
aged, but is usually dense and structurally homogeneous (Brown 1988,
Whitfield 1990, Sogge et al. 1993, Muiznieks et al. 1994).
Historically, E. t. extimus nested primarily in willows, buttonbush,
and Baccharis, with a scattered overstory of cottonwood (Grinnell and
Miller 1944, Phillips 1948, Whitmore 1977, Unitt 1987). Following
modern changes in riparian plant communities, E. t. extimus still nests
in native vegetation where available, but has been known to nest in
thickets dominated by tamarisk and Russian olive (Hubbard 1987, Brown
1988, Sogge et al. 1993, Muiznieks et al. 1994). Sedgwick and Knopf
(1992) found that sites selected as song perches by male willow
flycatchers (E. t. traillii/campestris) exhibited higher variability in
shrub size than did nest sites and often included large central shrubs.
Habitats not selected for either nesting or singing were narrower
riparian zones, with greater distances between willow patches and
individual willow plants. Nesting willow flycatchers of all subspecies
generally prefer areas with surface water nearby (Bent 1960, Stafford
and Valentine 1985, Harris et al. 1987), but E. t. extimus virtually
always nests near surface water or saturated soil (Phillips et al.
1964, Muiznieks et al. 1994). At some nest sites surface water may be
present early in the breeding season but only damp soil is present by
late June or early July (Muiznieks et al. 1994, M. Whitfield, Kern
River Research Center, in litt.-1993, J. and J. Griffith, Griffith
Wildlife Biology, in litt.-1993). Ultimately, a water table close
enough to the surface to support riparian vegetation is necessary.
Defining a minimum habitat patch size required to support a nesting
pair of E. t. extimus is difficult. Throughout its range, determining
the capability of habitat patches to support southwestern willow
flycatchers is confused by the species' rarity, unstable populations,
variations in habitat types, and other factors. However, the available
information indicates that habitat patches as small as 0.5 hectare (ha)
(1.23 acres) can support one or two nesting pairs. Sogge et al. (1993)
found territorial flycatchers in habitat patches ranging from 0.5 to
1.2 ha (1.23 to 2.96 acres). Two habitat patches of 0.5 and 0.9 ha
(1.23 and 2.2 acres) each supported two territories. Muiznieks et al.
(1994) also reported groups of territorial E. t. extimus in habitat
patches of approximately one to several hectares.
The nest is a compact cup of fiber, bark, and grass, typically with
feathers on the rim, lined with a layer of grass or other fine, silky
plant material, and often has plant material dangling from the bottom
(Harrison 1979). It is constructed in a fork or on a horizontal branch,
approximately 1-4.5 m (3.2-15 feet) above ground in a medium-sized bush
or small tree, with dense vegetation above and around the nest (Brown
1988, Whitfield 1990, Muiznieks et al. 1994).
The southwestern willow flycatcher is present and singing on
breeding territories by mid-May, although its presence and status is
often confused by the migrating individuals of northern subspecies
passing through E. t. extimus breeding habitat [D. Kreuper, Bureau of
Land Management (BLM), unpubl. data]. The southwestern willow
flycatcher builds nests and lays eggs in late May and early June and
fledges young in early to mid-July (Willard 1912, Ligon 1961, Brown
1988, Whitfield 1990, Sogge and Tibbitts 1992, Sogge et al. 1993,
Muiznieks et al. 1994). Some variation in these dates has been observed
(Carothers and Johnson 1975, Brown 1988, Muiznieks et al. 1994) and may
be related to altitude, latitude, and renesting.
The southwestern willow flycatcher is an insectivore. It forages
within and above dense riparian vegetation, taking insects on the wing
or gleaning them from foliage (Wheelock 1912, Bent 1960). It also
forages in areas adjacent to nest sites, which may be more open (M.
Sogge, National Biological Survey, pers. comm. 1993). No information is
available on specific prey species.
The migration routes and wintering grounds of E. t. extimus are not
well known. Empidonax flycatchers rarely sing during fall migration, so
that a means of distinguishing subspecies is not available (Blake 1953,
Peterson and Chalif 1973). However, willow flycatchers have been
reported to sing and defend winter territories in Mexico and Central
America (Gorski 1969, McCabe 1991). The southwestern willow flycatcher
most likely winters in Mexico, Central America, and perhaps northern
South America (Phillips 1948, Peterson 1990). However, the habitats it
uses on wintering grounds are unknown. Tropical deforestation may
restrict wintering habitat for this and other neotropical migratory
birds (Finch 1991, Sherry and Holmes 1993).
Breeding bird survey data for 1965 through 1979 combined the willow
and alder flycatchers into a ``Traill's flycatcher superspecies'',
because of taxonomic uncertainty during the 15-year reporting period.
These data showed fairly stable numbers in central and eastern North
America but strong declines in the West, the region including the range
of the southwestern willow flycatcher, and where the alder flycatcher
is absent (Robbins et al. 1986). [[Page 10697]]
Unitt (1987) reviewed historical and contemporary records of E. t.
extimus throughout its range, determining that it had ``declined
precipitously,'' and that ``although the data reveal no trend in the
past few years, the population is clearly much smaller now than 50
years ago, and no change in the factors responsible for the decline
seem likely.'' Data are now available that indicate continued declines,
poor reproductive performance, and/or continued threats for most
remaining populations (Brown 1991, Whitfield and Laymon, Kern River
Research Center, in litt. 1993, Sogge and Tibbitts 1992, Sogge et al.
1993, Muiznieks et al. 1994).

Previous Federal Actions

The Service included the southwestern willow flycatcher on its
Animal Notice of Review as a category 2 candidate species on January 6,
1989 (54 FR 554). A category 2 species is one for which listing may be
appropriate but for which additional biological information is needed.
After soliciting and reviewing additional information, the Service
elevated E. t. extimus to category 1 candidate status on November 21,
1991 (56 FR 58804). A category 1 species is one for which the Service
has on file substantial information to support listing, but for which a
proposal to list has not been issued because it is precluded at present
by other listing activity.
On January 25, 1992, a coalition of conservation organizations
(Suckling et al. 1992) petitioned the Service, requesting listing of E.
t. extimus as an endangered species under the Act. The petitioners also
requested emergency listing and designation of critical habitat. On
September 1, 1992, the Service published a finding (57 FR 39664) that
the petition presented substantial information indicating that listing
may be warranted and requested public comments and biological data on
the species. On July 23, 1993, the Service published a proposal (58 FR
39495) to list E. t. extimus as endangered with critical habitat, and
again requested public comments and biological data on the southwestern
willow flycatcher.

Summary of Comments and Recommendations
In the July 23, 1993, proposed rule (58 FR 39495) and associated
notifications, all interested parties were requested to submit comments
or information that might bear on whether to list the southwestern
willow flycatcher. The comment period was originally scheduled to close
October 21, 1993, then was extended to November 30, 1993. Appropriate
State agencies, county governments, Federal agencies, scientific
organizations, and other interested parties were contacted and
requested to comment. Newspaper notices inviting public comment were
published in the following newspapers; In California, Los Angeles
Times, L.A. Watts Times, Kern Valley Sun, and San Diego Union-Tribune;
in Arizona, Arizona Daily Sun, Arizona Republic, Tucson Daily Citizen,
White Mountain Independent, and Arizona Daily Star; in New Mexico,
Albuquerque Journal, Albuquerque Tribune, Santa Fe New Mexican,
Carlsbad Current-Argus, Silver City Daily Press; in Nevada, Las Vegas
Sun; in Colorado, Durango Herald; in Utah, Daily Spectrum; and in
Texas, El Paso Times. The inclusive dates of publications were August
31 through September 13, 1993, for the initial comment period and
October 28 through November 5, 1993, for the public hearings and
extension of public comment period.
The Service held six public hearings. Because of anticipated
interest in the proposed rule, the Service announced its intention to
hold at least three public hearings. In response to requests from the
public, three additional hearings were scheduled. A notice of the
hearing dates and locations was published in the Federal Register on
October 18, 1993 (58 FR 53702). Approximately 424 people attended the
hearings. About 17 people attended the hearing in Tucson, Arizona; 27
in Flagstaff, Arizona; 10 in Las Cruces, New Mexico; 12 in Albuquerque,
New Mexico; 350 in Lake Isabella, California; and 8 in San Diego,
California. Transcripts of these hearings are available for inspection
(see ADDRESSES).
A total of 3,102 written comment letters were received at the
Service's Ecological Services State Office in Arizona: 264 supported
the proposed listing; 2,650 opposed the proposed listing; and 188
expressed neither support nor opposition, but either commented on
information in the proposed rule, provided additional information, or
were non-substantive or irrelevant to the proposed listing.
Oral or written comments were received from 62 parties at the
hearings: 8 supported the proposed listing; 40 opposed the proposed
listing; and 14 expressed neither support nor opposition but provided
additional information, or were non-substantive or irrelevant to the
proposed listing.
In total, oral or written comments were received from 31 Federal
and State agencies and officials, 17 local officials, and 3,116 private
organizations, companies, and individuals. All comments received during
the comment period are addressed in the following summary. Comments of
a similar nature are grouped into a number of general issues.
Issue 1: The American Ornithologists' Union (AOU) did not list E.
t. extimus in its latest Checklist of North American Birds; Unitt
(1987) could not distinguish E. t. extimus by color or morphology;
genetic analysis is necessary to distinguish subspecies; significant
disagreement exists among scientists regarding taxonomy, for example,
McCabe (1991) did not recognize E. t. extimus; the willow flycatcher
subspecies, in fact the North American Empidonax flycatcher species are
too difficult to distinguish to make it reasonable to list subspecies
of those species; hybridization of the willow flycatcher subspecies
occurs; subspecies are not worth listing; E. t. extimus is a subspecies
of a very common species; E. t. extimus is not worth listing because it
is one of nine common species in the genus Empidonax; this subspecies
and subspecies in general are of minor ecological value; their loss
would be unimportant; there is little value in preserving rare species/
subspecies; and historical taxonomic questions may confuse population
trend information.
Service Response: The Service has determined that E. t. extimus is
a valid taxon. The Service relies on the most current and authoritative
data available in making decisions regarding the validity of species,
subspecies, or distinct vertebrate population segments. These data
include articles published in professional journals, agency reports,
and other unpublished data provided by researchers. For the
southwestern willow flycatcher, the Service reviewed this information
and found a majority opinion that E. t. extimus is a valid subspecies.
Authorities who critically examined the taxonomy of E. traillii and
recognized E. t. extimus include Phillips (1948), Aldrich (1951),
Hubbard (1987), Unitt (1987), and Browning (1993). Other authorities
accepting the subspecies include Behle and Higgins (1959), Phillips et
al. (1964), Bailey and Niedrach (1965), Oberholser (1974), Monson and
Phillips (1981), Harris et al. (1987), Schlorff (1990), Whitfield
(1990), Brown (1991), Harris (1991), Western Foundation for Vertebrate
Zoology in litt. 1993, University of California in litt. 1993. The AOU
(1983) did not list subspecies of any bird, including the willow
flycatcher, in its 1983 Checklist of North America Birds. However, this
does not indicate a lack of recognition of E. t. extimus, or for the
concept of subspecies. The preface to the 1983 Checklist states ``The
Committee [[Page 10698]] strongly endorses the concept of the
subspecies * * * and we wish to make it clear that the omission of
separate listings of subspecies in this edition is not a rejection of
the validity or utility of this systematic category * * *.''
The Service noted McCabe's (1991) consideration of the willow and
alder (E. alnorum) flycatchers as a single species, and his reluctance
to recognize willow flycatcher subspecies. McCabe (1991) provides a
thorough review of the history of E. alnorum and E. traillii taxonomy,
and the questions of ecological, morphological, and song-type
distinction on which this taxonomic evaluation has been based. However,
the Service agrees with Sedgwick's (1993) comments and McCabe's own
observation that McCabe (1991) contrasts with the majority opinion
regarding taxonomy of the willow and alder flycatchers.
After examining 305 study skins, Unitt (1987) found that while four
subspecies (E. t. traillii, E. t. adastus, E. t. brewsteri, and E. t.
extimus) could be tentatively separated by the ``75 percent rule''
using overall size (wing and tail lengths and their ratios to one
another), these criteria were not satisfactorily conclusive. However,
he found that the subspecies could be satisfactorily distinguished,
under the ``75 percent rule,'' using color, wing formula (relative
lengths of primary wing feathers), or both. Browning (1993) examined
270 specimens and found that all four subspecies, and a fifth (E. t.
campestris) were distinguishable by color.
The Service acknowledges that taxonomy of E. traillii races
continues to pose questions and may be revised in the future. The
Service has determined that E. t. extimus is a sufficiently distinct
entity to be listed under the Act at the very least as a distinct
vertebrate population [50 CFR Sec. 424.02(k)]. However, the Service
accepts the majority opinion that E. t. extimus is a valid subspecies
and lists it as such.
The Service considers taxonomic distinctness in assigning
priorities for species listings, but not in determining whether or not
to list species. The Act authorizes listing of species, subspecies, or
distinct population segments, all of which have ecological
significance.
Issue 2: The southwestern willow flycatcher is not a riparian
obligate species. It also occurs in open prairie woodlots, dry and
brushy pastures, and brushy fields or slopes. No surveys of dry
habitats have been done to prove riparian obligacy. The southwestern
willow flycatcher does not ``invariably'' nest near surface water.
Service Response: The Service is unaware of any study, report, or
species account that describes E. t. extimus as anything but a riparian
obligate. No commenter provided data, studies, or reports indicating
that E. t. extimus nests outside riparian habitats. Several commenters
cited field guides which describe the willow flycatcher (all
subspecies) as occurring ``* * * in drier situations (than the alder
flycatcher) * * *'' (Peterson 1990), ``* * * on brushy slopes * * *''
(Robbins et al. 1983), and ``* * * dry, brushy upland pastures * * *''
(National Geographic Society 1990). The Service believes that field
guide species accounts do not constitute the best available scientific
information on biology, ecology or habitat requirements. Field guide
accounts tend to be brief and generalized, and in this case represent
habitat use of other willow flycatcher subspecies, which occur in more
mesic regions. Similarly, Barlow and McGillivray's (1983) description
of willow flycatchers (E. t. campestris/traillii) selecting ``* * * a
more xeric upland habitat * * *'' in Ontario, Canada, is not considered
relevant to habitat selection of E. t. extimus in the desert Southwest.
In the wetter climates of the north, upper midwest, and northeast,
habitat conditions of moist soil or surface water, supporting thickets
of deciduous shrubs and trees, are not restricted to riparian areas.
However, in the arid Southwest where E. t. extimus occurs, these
conditions are limited to riparian areas, usually in profound contrast
to the adjacent and prevailing desert conditions. Various authors
(e.g., King 1955) have noted that while willow flycatchers may nest
away from riparian areas in the north and east, in arid regions (the
ranges of E. t. brewsteri and E. t. extimus particularly) the species
is restricted to riparian habitats. Regarding the presence of surface
water during the breeding season, new information was provided
indicating that some nest sites have surface water in close proximity
early in the breeding season, which recedes underground by the end of
the breeding season. At these sites, the water table remains at least
high enough to sustain riparian vegetation. The Service is unaware of
any surveys performed in non-riparian habitats specifically to verify
the absence of nesting E. t. extimus. However, the Service relied on
local, State, and regional species accounts of distribution and habitat
use, none of which describe occurrence outside of riparian habitats.
Issue 3: The loss and modification of southwestern riparian habitat
is overstated, poorly documented, and does not constitute a threat to
the flycatcher; the statement that 90 percent loss of riparian habitat
has occurred is inaccurate and an exaggeration; riparian habitat has
not decreased, but increased as a result of diversions, irrigation,
etc; habitat has increased, not decreased, in local area(s) over the
past 20 years; riparian regeneration is approaching 1,000 percent in
southeastern Arizona; Hastings and Turner (1965) show that cottonwood
riparian habitat has increased in southeastern Arizona; the upper San
Pedro River is recovered, not ``unsuitable and unoccupied'' as the
Service claimed; because tamarisk has increased, and E. t. extimus uses
tamarisk, tamarisk invasion does not constitute modification of
habitat, but expansion of habitat; population declines in the past 20
years are concurrent with improved riparian habitats, so no correlation
exists between trends in habitat and populations; the proposal fails to
support claims that urban development, agriculture, and livestock
grazing are harmful to the flycatcher.
Service Response: The Service has determined that the documentation
of loss and modification of southwestern riparian habitats, cited in
this final rule, is adequate. Regarding the ``90 percent loss and
modification'' statement, the proposed rule stated that ``* * * as much
as 90 percent * * *'' (emphasis added) has been lost or modified. The
actual percentage lost or modified is not expected to be consistent
across the region, but should vary with elevation, rainfall, geographic
area, relative size of drainage system, and severity of impacts. Loss
and modification may be lesser at higher elevations, where
precipitation is greater and evaporation less. In most major lower
elevation desert riparian systems, loss or modification may in fact be
near 100 percent, e.g., the lower Colorado, lower Gila, lower Rio
Grande, and lower Salt Rivers. Because ``modification'' includes
alterations in flow regimes, channel confinement, changes in water
quality, and floristic makeup of riparian systems, the Service believes
it is not a misrepresentation to state that up to 90 percent of
southwestern riparian ecosystems have been lost or modified.
Commenters stating that riparian habitat has not decreased, but
increased as a result of diversions and irrigation, presented no
supporting information. The Service recognizes that some diversions,
particularly unmaintained irrigation ditches, sometimes support
riparian vegetation. However, the Service believes diversion and
irrigation result in a net loss of riparian habitat.
[[Page 10699]] Where riparian vegetation becomes established along
irrigation systems, it is often cleared away at regular intervals.
Where it is not, it is sometimes because an artificially created
riparian/wetland habitat is being maintained as mitigation or
compensation for loss of natural riparian habitat elsewhere.
The Service recognizes that in some local areas in recent decades,
riparian habitat has been rehabilitated or increased, not decreased.
However, the Service accepts the consensus of literature cited in this
rule that the overall trend continues to be one of habitat loss.
Hastings and Turner (1965) and Bahre (1991) noted that riparian
habitats were already significantly altered by the turn of the last
century. Hastings and Turner (1965) also noted that all major
watercourses in southern Arizona suffered entrenchment and became more
ephemeral in flow in approximately 1890. Land use practices that had
already affected riparian habitats in this Arizona-Mexico border region
included livestock grazing, woodcutting, and water diversion; climatic
changes may also have contributed. The differences between the historic
and more recent photographs show some riparian recovery, concurrent
with reductions in livestock stocking levels from their highs in the
late 1800's. No data, or elaboration, were presented to support
statements that riparian regeneration is approaching 1000 percent in
southeastern Arizona.
As this final rules discusses, E. t. extimus sometimes nests in
tamarisk, but does so at lower densities, and apparently at lower
success rates than in native vegetation (Hunter et al. 1988, Sogge et
al. 1993, Muiznieks et al. 1994). Therefore, tamarisk invasion likely
represents replacement of native habitat with lower-quality habitat,
rather than an increase in habitat availability. Only in a few unique
situations does tamarisk truly represent ``new'' habitat. For example,
in the Grand Canyon flycatchers nest in a ``new'' riparian habitat,
dominated by tamarisk (Carothers and Brown 1991). This new riparian
habitat became established in the historic flood-scour zone of the
Colorado River, after construction of Glen Canyon Dam eliminated annual
scouring floods. However, flycatchers nest in this area in low numbers
(Brown 1991, Sogge and Tibbitts 1992, Sogge et al. 1993) and have low
nesting success. It is noteworthy that by forming Lake Powell, Glen
Canyon Dam also inundated habitat in Glen Canyon. The southwestern
willow flycatcher was described as a common nester in Glen Canyon prior
to inundation (Behle and Higgins 1959, Behle 1985), indicating that
this historic habitat was of higher quality than the new habitat in
Grand Canyon.
Issue 4: The flycatcher has always been a rare bird, so its rarity
now is no change from historical situations; historical specimens are
few, indicating the bird was always rare; population data are
insufficient to show decline; population data are suspect, developed by
parties with agendas of land control/acquisition; the flycatcher is not
declining in all areas; historical taxonomic questions may confuse
population trend information; accuracy or existence of population trend
data for the last 50 years is questionable; population sampling
techniques were not discussed; these could bias trend studies;
population data are incomplete; the proposal relies on data reflecting
loss of habitat rather than comprehensive population trend analysis;
there are no recent collections of E. t. extimus from southern Arizona
riparian areas.
Service Response: The Service agrees that the flycatcher has
probably always been sparsely distributed, as a function of the sparse
distribution of its wetland habitat in a predominantly xeric region.
However, sparse distribution and rarity are not necessarily equivalent.
At individual locales the flycatcher may occur in considerable numbers,
as indicated by Herbert Brown's collection of 36 nests near Yuma in
1902, and the persistence of several populations of considerable
numbers (30-40 pairs) in relatively small areas like the Kern River
Preserve in California (Harris et al. 1986, Whitfield 1990). Although
E. t. extimus habitat is rare, where it is present nesting pairs may
occur in relatively high densities. This phenomenon has caused some
authors to describe E. t. extimus as something of a colonial nester
(e.g., Unitt 1987).
Regarding the lack of historic or recent specimens available from
various parts of the bird's range, the Service notes that specimen
collection is largely a function of collecting activity, not simple
presence of the subject.
The Service agrees that, as with many non-game species, population
trend data are incomplete. No wide scale, and few local studies have
been funded or undertaken to track this species through time.
Comprehensive, long-term population data are not necessarily required
for making listing determinations. Rather, these decisions often rest
upon data on loss and modification of habitat and other threats, which
are reasonably assumed to result in population declines. In many cases,
population declines are inferred from decline in habitat availability.
However, in this and other listing determinations, the Service seeks to
measure such inference against whatever population trend data are
available. Regarding concerns over sources of these data, the Service
endeavors to verify accuracy and credibility of data. The reports
published by government agencies, academic institutions, and
professional journals on which this determination is based are accepted
as credible. To interpret population trends in the light of changing
taxonomic status, the Service considered all information for willow
flycatchers in the current range of E. t. extimus to be relevant.
Issue 5: Livestock grazing is not a threat to E. t. extimus or its
habitat; Montgomery et al. (1985) found 53 singing birds in a grazed
area in New Mexico; on Marine Corps Base Camp Pendleton, E. t. extimus
is increasing where sheep graze; nest disturbance by cattle is
unsubstantiated; southwestern flora evolved with large grazing
ungulates; the proposed rule lacks examples of flycatcher status
improving with reduction in livestock or improved livestock management;
E. t. extimus is not improving in areas with no grazing; the proposed
rule equates any livestock grazing with overgrazing, and fails to
distinguish between overgrazing and well-managed grazing; proper
livestock management is compatible with healthy riparian habitat; some
level of livestock grazing is compatible with/necessary for healthy
riparian ecosystems; willows are brush, which cattle don't eat, but
cattle are blamed for both brush encroachment and brush destruction;
cattle trample stream banks, which allows water to escape, creating
more riparian habitat; livestock grazing prevents urbanization of land,
which would have a greater impact on riparian habitats.
Service Response: The proposed and final rules discuss overuse by
livestock as a threat to E. t. extimus, through impacts on riparian
habitat. The Service recognizes that what constitutes ``overuse''
varies with differing riparian ecosystems, elevation, type of
livestock, seasonality of use, and other factors. The Service believes
that some livestock grazing regimes are likely to be found compatible
with rehabilitation and maintenance of E. t. extimus habitat.
Montgomery et al. (1985) did not determine whether the willow
flycatchers they detected on grazed land were resident E. t. extimus or
migrating individuals of other subspecies. Further, neither grazing
intensity nor nesting [[Page 10700]] success were quantified, so that
no correlations can be made. On Camp Pendleton, increases in E. t.
extimus were concurrent with livestock (sheep) grazing but also with an
extensive cowbird trapping program (Griffith and Griffith 1993).
Finally, as discussed in this rule, examples exist of E. t. extimus
(and other E. traillii subspecies) numbers and habitat increasing as a
result of grazing reductions or other improvements in livestock
management.
The Service recognizes that southwestern riparian ecosystems
evolved with native grazing ungulates (e.g., deer and elk). However,
domestic livestock do not forage, herd or move in the same manner as
native species. Further, elk occur at higher elevations of the
Southwest, and are absent from the lowland river systems that
constitute the majority of E. t. extimus habitat.
Issue 6: Timber harvesting is not a threat to the flycatcher's
riparian habitat.
Service Response: The proposed rule noted that the petitioners
claimed timber harvest caused watershed changes which could result in
damage to riparian habitats through increasing intensity and frequency
of floods. The petitioners presented no specific information on this
claim. A number of experimental treatments on Southwestern forested
watersheds have demonstrated increased peak and flood flows as a result
of timber harvest (Tecle 1991). The degree to which timber harvesting
has affected riparian habitats inhabited by the willow flycatcher,
however, has not been quantified and is unknown. The Service did not
implicate timber harvesting in the proposed rule as a major cause of
riparian habitat loss. Rather, it pointed to that activity as one of
many factors potentially responsible for riparian habitat loss and
modification. Pending new information demonstrating otherwise, the
Service still considers timber harvesting a potential threat to
riparian habitat through loss and modification. However, the Service
does not believe that this threat exists rangewide, nor does it believe
that timber harvesting alone is responsible for riparian habitat loss
or the endangered status of the southwestern willow flycatcher.
All causal factors will be addressed in the recovery planning
process, and through the Act's section 7 consultation process, through
which Federal agencies will be responsible for evaluating the effects
of activities such as timber harvest on the flycatcher's riparian
habitat.
Issue 7: Water impoundments have been beneficial, not detrimental;
fluctuating flows below dams are not detrimental, in fact have
increased riparian habitat (Glen Canyon Dam resulted in creation of
riparian habitat in Grand Canyon); impoundments protect habitat by
preventing catastrophic floods; the proposal had inadequate discussion
of water impoundments as threat.
Service Response: As discussed elsewhere in this final rule, water
impoundments have a variety of effects on riparian habitats. The
Service has determined that, with respect to E. t. extimus, the net
effect of these influences is negative. For example, Glen Canyon Dam
eliminated massive annual scouring floods in the Grand Canyon. This
resulted in the development of a new riparian zone dominated by
tamarisk (Carothers and Brown 1991). However, flycatchers nest there in
very low numbers and with low nesting success (Brown 1991, Sogge and
Tibbitts 1992, Sogge et al. 1993). In contrast, E. t. extimus was
described as a common nester in Glen Canyon (Behle and Higgins 1959,
Behle 1985), prior to its inundation by Lake Powell.
Issue 8: Comments concerning the ecology of cowbirds and cowbird
parasitism included the following: Breeding Bird Survey (BBS) data
indicate that cowbirds have declined, not increased; the claim that
cowbirds are associated with livestock is not supported; cowbirds are
associated with deer and elk, not cows; the cowbird threat is a natural
one; there is inconclusive evidence that cowbird increases are directly
connected with livestock grazing; cowbird parasitism of E. t. extimus
is known in areas without livestock grazing (e.g., Grand Canyon, Kern
River); there is no correlation between livestock grazing in riparian
areas and cowbird parasitism; Taylor (1986) showed that cowbirds were
most abundant in areas with long-term livestock exclusion; because
flycatchers and cowbirds are positively associated (they tend to occur
together), flycatchers can coexist with cowbirds; there is inconclusive
evidence that cowbird parasitism is responsible for declines in nesting
success; cowbirds have increased as a result of increases in bird
feeders, campgrounds, etc. and increases in wintering food/habitat; the
proposed rule cited no studies that documented cowbird parasitism of E.
t. extimus; citations regarding parasitism of other species are
irrelevant. Section 4(a)(1)(E) of the Act allows listing species
because of ``* * * natural or manmade factors affecting its continued
existence * * *.''
Service Response: Cowbird numbers appear to be declining only in
the northeastern United States and southeastern Canada. Through the 27
years of the BBS, cowbird populations have remained fairly stable, with
a small increase in the 1970's, small decrease in the 1980's, and
slight increase in recent years; however, the West has experienced a
marked population increase over the last five years (Wiedenfeld 1993).
The association of cowbirds with domestic livestock is detailed in
the sources cited in this final rule. The Service has neither found nor
been provided information indicating that cowbirds are associated with
deer or elk. Other factors, including habitat fragmentation and urban/
suburban feeding, are likely to have contributed to increases in
cowbirds. These causal factors will be important to address in the
section 7 consultation process and the development of recovery actions.
However, it is the threat of parasitism, regardless of cause, that in
part necessitates listing.
Where high parasitism rates are found in E. t. extimus nesting
locations in areas with no livestock grazing at the nest site, there
have been livestock nearby that provide feeding sites in close enough
proximity to facilitate cowbird parasitism. Cowbirds may disperse up to
7 kilometers (km) from their daily feeding/roosting sites to areas with
host species (Rothstein et al. 1984). At the Kern River Preserve, the
riparian habitat supporting E. t. extimus is not grazed, but the
immediately adjacent lands are. Similarly, although livestock grazing
does not occur in Grand Canyon National Park, open range grazing and an
introduced bison herd occur on adjacent lands. Further, cowbirds
concentrate at pack animal corrals at various points within the
National Park (Johnson and Sogge 1993). Thus, flycatcher habitat may be
ungrazed but still be affected by cowbirds, by having livestock
concentrations nearby to serve as cowbird feeding sites.
Cowbirds and E. t. extimus are positively associated because
cowbirds require, and therefore associate with, prospective hosts. The
Service finds that extensive information indicates cowbird parasitism
negatively affects the southwestern willow flycatcher. This information
includes specific examples of parasitism of E. t. extimus, cited in
this rule, and examples of the effects of cowbird parasitism on other
rare species of limited habitat. Recent information continues to
document high parasitism rates for E. t. extimus (Sogge et al. 1993,
Muiznieks et al. 1994), and increases in flycatcher reproduction or
populations, concurrent with reductions in cowbird numbers (Griffith
and Griffith 1993, M. Whitfield in litt.--1993). [[Page 10701]]
Issue 9: Tamarisk is not an invader species, but a successional
stage, becoming established on recently-scoured areas; livestock do eat
tamarisk for its salt content; the Service needs to clarify the
positive and negative characteristics of tamarisk; tamarisk increases
habitat availability, in fact provides high-quality bird habitat.
Service Response: The Service found no information, and was not
provided any information by commenters, indicating that tamarisk is
primarily a successional stage vegetation type, rather than an invasive
exotic. This final rule presents an updated discussion of tamarisk
ecology, supported by additional literature references. The Service
concurs with the consensus among published authorities that tamarisk is
an invasive, usually dominant exotic plant, not a successional species.
Commenters that stated livestock eat tamarisk for its salt content
provided no supporting information. The Service's understanding of the
literature is that cattle prefer native species over tamarisk for
forage.
As discussed in this rule, E. t. extimus has been documented
nesting in tamarisk at elevations above approximately 625 m (2000
feet). Rather than attempt to present criteria here for when tamarisk
eradication presents a threat or a positive recovery action, the
Service will address this issue on a case-by-case basis through the
section 7 consultation process with other Federal agencies. This will
allow Federal agencies the flexibility to consider individual cases in
the light of the specific circumstances surrounding each one.
Although Brown and Trosset (1989) suggested that tamarisk provided
an ``ecological equivalent'' to native vegetation, they qualified this
statement. They noted that their study involved small sample sizes, and
that their methods differed from Whitmore's (1975, 1977), which was
their basis for comparison with native riparian habitats. Further,
Brown and Trosset (1989) noted that this ``ecological equivalent''
function may be most significant where tamarisk became established
where no native riparian vegetation existed previously (e.g., the
Colorado River in Grand Canyon).
Issue 10: Herbert Brown's collection of 36 nests with eggs from the
lower Colorado River, in 1900 and 1902, indicates overcollection for
science may have caused declines.
Service Response: The effects of Brown's collections on populations
over 90 years ago are unknown. These effects may have been significant.
However, Brown's collections themselves may suggest that populations at
that time could sustain such collecting pressure. The origin of Brown's
collections from several specific locales suggests that E. t. extimus
was an abundant nesting bird in the area of the confluence of the Gila
and Colorado rivers. Collection of 36 nests would have impacted
reproduction alone, only for 1902, when all but one of the nests was
collected. Considering continued habitat loss, and increasing cowbird
populations since 1902, the Service does not believe that Brown's
collection of 36 nests with eggs in 1900 and 1902 significantly affects
E. t. extimus populations in 1995. However, the Service believes that
current flycatcher populations are unlikely to be able to sustain
collecting pressures like Brown's activities of 1902. In 1993,
extensive surveys of the region of Brown's collections located only
four to five territories (Muiznieks et al. 1994).
Issue 11: Drought has impacted habitat.
Service Response: The Service recognizes that extended droughts are
likely to have impacted E. t. extimus through habitat reduction. This
natural phenomenon and human-induced habitat impacts may exacerbate one
another's effects on E. t. extimus habitat.
Issue 12: Predators such as snakes, hawks, ravens, grackles, and
domestic cats are threats to E. t. extimus.
Service Response: The Service agrees that these constitute
potential predators of songbirds, including E. t. extimus. While
predation would not normally be expected to be a major threat to the
flycatcher, its populations may be so low currently that they cannot
withstand normal predation. Further, several of these types of
predation may be facilitated by habitat alteration or other human
actions. Therefore, the Service will address predation in recovery
planning, and other Federal agencies should consider the effects of
their actions on some of these forms of predation.
Issue 13: Hikers, elk, deer, and beaver are threats to flycatcher
nests and habitat; listing would cause restrictions on fishing and
water recreation.
Service Response: No information was provided to support statements
that hikers constitute a threat to E. t. extimus. This rule briefly
discusses possible impacts of recreation on E. t. extimus and its
habitat. These impacts are expected to be primarily effects on
vegetation through soil compaction, clearing vegetation, and creating
trails. Because E. t. extimus is not a timid species, disturbance is
expected to be an impact only when continuous intrusive activities take
place near habitat, or when recreation takes place within or adjacent
to the nest stand. Because nest stands tend to be very dense, virtually
impenetrable thickets, often with swampy conditions, recreational
impacts are not expected to occur often.
Elk and deer use riparian habitats for foraging, but generally
behave differently than domestic livestock. They tend not to occur in
large concentrations and remain in riparian areas for long periods like
domestic cattle. The Service is aware that elk can impact riparian
systems when their numbers reach high levels. However, elk are lacking
from the majority of southwestern willow flycatcher habitats, because
these riparian areas occur at lower elevations than elk. Beaver cut and
use willow and cottonwood, but may also be important in creating quiet-
water riparian habitats by damming smaller and steeper creeks.
Issue 14: The presence of unoccupied habitat indicates that E. t.
extimus is not currently habitat limited.
Service Response: As discussed in this rule, the Service has
determined that E. t. extimus has suffered extensive habitat loss,
which is complicated by the current low number of flycatchers, and
reduction of reproductive output due to brood parasitism by brown-
headed cowbirds. The current existence of apparently suitable habitat
that is not occupied by E. t. extimus more likely indicates that its
numbers are too low to fill all available habitat. Further, habitat
exists in isolated, fragmented patches. With low population numbers and
inhibited reproduction, E. t. extimus may be unable to maintain local
populations, much less be able to disperse and colonize unoccupied
locales.
Issue 15: Cowbird parasitism is the main threat to E. t. extimus,
not habitat loss; cowbird control is the primary recovery need, not
habitat protection; cowbird trapping would eliminate the need for
designating critical habitat; the Service should implement and fund
cowbird control programs instead of listing.
Service Response: The Service has determined that cowbird
parasitism is one of several primary threats to E. t. extimus, which
also includes the loss and modification of habitat. Cowbird parasitism
and loss and modification of habitat are interrelated. Cowbird
parasitism is a function not just of cowbird abundance, but also
habitat quality. Potential host species in degraded, fragmented habitat
are more susceptible to nest parasitism than those nesting in larger
tracts of dense, contiguous habitat. Cowbird parasitism
[[Page 10702]] will probably remain an imminent threat until habitat
rehabilitation is accomplished. The Service acknowledges that cowbird
control should be an immediate, high priority recovery action. However,
cowbird control is a ``stop-gap'' action. Rehabilitating riparian
habitat to make E. t. extimus and other riparian birds less susceptible
to cowbird parasitism will be necessary for a long-term solution.
Ultimately, the ranking of threats in order of severity is not relevant
to the listing question. It is because a number of often interdependent
threats exist that listing E. t. extimus is necessary. Ranking threats
in order of severity and addressing them accordingly will be part of
the recovery process.
Issue 16: Willow flycatchers nesting in the northern States,
Alaska, and Canada are subspecies other than E. t. extimus. The
boundaries of the breeding range of E. t. extimus should be expanded to
include the Santa Ynez River in California, and the Green and Colorado
River systems in west-central Utah; E. t. extimus does not occur in
Utah, Colorado, or the Carson National Forest in northern New Mexico;
the willow flycatcher is common in the northern States, Alaska, Canada,
most of the U.S., Mexico and Panama; caution should be exercised in
defining range limits of the subspecies, including elevational limits.
Service Response: Two primary authorities (Unitt 1987, Browning
1993) provide the range limits of E. t. extimus identified in this rule
(see Figure 1). The Service also considered other information, such as
historical nesting records, habitat characteristics, and proximity to
neighboring populations of E. t. extimus or other willow flycatcher
subspecies. Using this information, the Service provisionally defines
the northwestern limit of the subspecies' range to be the Santa Ynez
River in California. Willow flycatchers nesting along the Santa Ynez
River occupy lowland riparian habitat similar to other coastal
California locations of E. t. extimus, and few willow flycatcher (i.e.,
E. t. brewsteri) nesting locales are known in coastal California for a
considerable distance north of the Santa Ynez River.
Browning (1993) found no evidence of intergrades between E. t.
extimus and E. t. adastus in Utah. The northern limit of E. t. extimus
in Utah is believed to correspond closely to the area comprising the
following counties: Garfield, Kane, San Juan, Washington, and Wayne.
This area takes in stretches of riverine riparian habitat in southern
Utah that have historical records of flycatchers and that still have
potential willow flycatcher habitat.
The Service recognizes that taxonomic questions may arise
concerning flycatchers occupying some high-elevation locales within the
range of E. t. extimus. Because the genetic relatedness of willow
flycatchers breeding at some high elevation areas, such as the White
Mountains of Arizona, may be substantial, willow flycatchers in those
locales should be considered E. t. extimus until further research
demonstrates otherwise. Protection of these breeding groups could be
critical for population recovery, immigration, and exchange of genetic
material within a highly-fragmented landscape.
Issue 17: It is inappropriate to use data from E. t. brewsteri and
E. t. adastus to support listing E. t. extimus; information cited on
livestock damaging nests comes from other subspecies.
Service Response: The Service carefully considered the propriety of
using information on other willow flycatcher subspecies in evaluating
the listing question for E. t. extimus. In applying such information,
the Service considered ecological similarities and dissimilarities
between the subspecies. The Service believes that data from other
subspecies are applicable in some cases, but not others. The Service
has identified which subspecies provided data sources throughout the
proposed and final rules. The phenomenon of livestock damaging nests
and/or contents through physical contact is known for willow flycatcher
subspecies other than E. t. extimus. This threat was noted to recognize
that the potential exists, where nests occur low enough in vegetation
or in other vulnerable locations, that livestock, humans, or other
animals may contact them or the nest plant.
Issue 18: Habitat in California was lost to urbanization, not
livestock; the proposed rule had inadequate discussion of urban and
suburban development as a threat; urban development is not a threat to
some populations.
Service Response: Loss and modification of the riparian habitat of
E. t. extimus is the result of numerous factors, discussed in depth in
this rule. Not all these factors have affected all riparian habitats,
and some rare habitats remain unaffected. Further, the degree to which
these factors influence riparian habitat varies across the landscape.
Urban and suburban development has certainly impacted some E. t.
extimus habitats. These impacts may result from direct encroachment and
channelization of riparian habitats, as in coastal southern California
and central Arizona. Urban and suburban development also increase
demands on river systems for water and hydropower. Thus, expanding
urban centers can result in dewatering or alteration of riparian
systems tens or hundreds of miles away. For example, the water and
power demands of Los Angeles, Phoenix and Las Vegas result in effects
on the Colorado River hundreds of miles from any of these cities.
Issue 19: The primary threat to E. t. extimus is loss of wintering
habitat in Central and South America, or other factors along migration
routes; the proposed rule contained insufficient information on
migration studies; protecting breeding grounds is not logical, because
E. t. extimus spends eight months of the year in migration or on
wintering grounds.
Service Response: Although tropical deforestation possibly may
restrict wintering habitat of the willow flycatcher, the best available
current information on the subject suggests otherwise. The limited data
on willow flycatcher wintering habitat indicates that this species uses
``* * * brushy savannah edges and second growth'' in Costa Rica (Stiles
and Skutch 1989); in Panama it has been documented in ``shrubby areas''
(Ridgely 1981); and in South America it has been documented in ``* * *
shrubby clearings, pastures, and lighter woodland'' or ``* * * on
islands with early successional growth'' (Ridgely and Tudor 1994).
Given existing land use practices in Central and South America, which
are characterized by conversion of old-growth forested habitat to
agricultural and second-growth habitats, few if any of the winter
habitat types in which willow flycatchers have been documented should
currently be in jeopardy.
Issue 20: The Service cannot define nesting habitat; habitat
requirements are poorly understood; the proposed rule's description of
nesting habitat is flawed and inadequate to direct management; the
minimum patch size necessary to support a nesting pair of E. t. extimus
is 1 to 1.5 hectares.
Service Response: The Service believes the proposed rule and this
final rule accurately compile and summarize the existing information on
E. t. extimus nesting habitat, and that information is sufficient to
identify, conserve, and recover the riparian ecosystem of which E. t.
extimus is a part. Habitat patches occupied by E. t. extimus vary
somewhat in size, floristic composition, vegetation structure, and type
of wetland. Therefore, the Service believes it is inappropriate and
inaccurate to [[Page 10703]] narrowly define suitable habitat in terms
of plants per unit area, vegetation density, specific plant community
composition, type and volume of surface water, and patch size. The
Service has no information to indicate inaccuracy or inadequacy of the
habitat description presented in this rule. Specifically regarding
patch sizes, one to two E. t. extimus pairs have been observed nesting
in habitat patches of 0.5 ha (Sogge et al. 1993, Sogge et al. unpubl.
1994 data); therefore 1.0 to 1.5 ha is not an accurate estimate of the
minimum patch size needed to support a single nesting pair.
Issue 21: Habitats used by nesting pairs differ from those used by
single, unmated, wandering, or migrant flycatchers; the latter face
minimal threats and are not essential to conservation of the species.
Service Response: The commenters provided no data supporting the
statement that habitats used by unpaired E. t. extimus differ from
nesting habitat, and the Service found no indication of this in the
available literature. Unmated, resident E. t. extimus have been found
in habitats identical to nearby habitats occupied by nesting pairs
(Sogge and Tibbitts 1992, Sogge et al. 1993). The Service believes that
single, unmated E. t. extimus also face threats of habitat loss, and
that conservation of these individuals is essential to the conservation
of the species, particularly at the low current numbers of flycatchers.
Issue 22: Listing constitutes single-species management that will
damage other species; E. t. extimus habitat is incompatible with
habitat needs of other listed and sensitive species, particularly the
spikedace and loach minnow.
Service Response: The purposes of the Act are to provide a program
for the conservation of threatened and endangered species and to
conserve the ecosystems upon which threatened and endangered species
depend. The Service believes that managing for E. t. extimus and other
listed riparian and aquatic species accomplishes this purpose, to the
mutual benefit of listed and nonlisted species alike. The intent of
this listing is to conserve and recover E. t. extimus and the riparian
and aquatic ecosystems of which it is a part.
The primary constituent elements of critical habitat described for
the spikedace (59 FR 10906) and loach minnow (59 FR 10898) are not in
conflict with the habitat requirements for the southwestern willow
flycatcher, and are not in conflict with the primary constituent
elements of its proposed critical habitat (58 FR 39495). The fishes
require ``a healthy, intact riparian community,'' which will also
benefit E. t. extimus and other riparian and aquatic species. The
spikedace, loach minnow, and E. t. extimus all require surface water
and/or a high water table, a low to moderate stream gradient, and
periodic flooding. The fishes specifically require a ``natural,
unregulated hydrograph,'' which the Service believes would also benefit
the flycatcher. These fish also require moderate to high bank
stability; maintenance of the riparian vegetation on which E. t.
extimus depends will provide such bank stability. The Service does not
view management for E. t. extimus, spikedace, and loach minnow as
mutually exclusive, but as mutually beneficial.
Issue 23: Floods regenerate habitat, they do not destroy it; floods
destroy habitat; floods, not livestock, caused much of riparian
degradation; the proposed rule is confusing and contradictory on the
role of floods as a threat or necessary ecological function.
Service Response: The proposed rule stated that ``Its habitat
rarity, and small, isolated populations make the remaining E. t.
extimus increasingly susceptible to local extirpation through
stochastic events such as floods * * *. In early 1993, catastrophic
floods in southern California and Arizona damaged or destroyed much of
the remaining occupied or potential breeding habitat. Historically,
these floods have always destroyed habitat but were also important
events in regenerating cottonwood-willow communities.''
It is important to note that E. t. extimus is threatened by
stochastic events like floods because of its current rarity and
isolated nature of populations. If the species existed at healthy
population levels, and if its riparian habitat were not greatly
reduced, these natural stochastic events would not constitute threats.
The 1993 flood events referred to were extraordinary in nature,
described regionally as 500-year floods. Therefore, they do not typify
flood events in the river systems involved. Further, while natural
flood events are expected to destroy some flycatcher habitat, they are
also crucial for regenerating natural riparian nesting habitat. In a
healthy system where riparian vegetation is abundant and the stream
channel is not eroded or destabilized, destruction and regeneration are
balanced and habitat is generally available. Only when riparian
vegetation is severely reduced and the stream channel and watershed are
destabilized are riparian and aquatic species threatened by the
natural, short-term habitat losses resulting from flooding.
Issue 24: To manage for E. t. extimus, the Service will enforce or
has proposed a fenced livestock-free corridor.
Service Response: The Service has neither proposed nor been
consulted regarding a fenced, livestock-free corridor established along
riparian areas on State, Federal, or private lands.
Issue 25: Beneficial land management practices should be recognized
and discussed; the proposed rule fails to acknowledge that some
habitats are protected from urban development.
Service Response: The Service recognizes that some management
practices are beneficial. Some practices have protected or improved
habitat, resulted in expanded populations, and/or improved
reproduction. The Service will look to these beneficial land management
practices as important examples in the recovery planning process.
However, in making a listing determination the Service must consider
the situation across the species' entire range. It is this overall
perspective that drives the listing decision. Although some nesting
groups of E. t. extimus may be safe, stable, or perhaps even
increasing, the Service has determined that overall the species is
endangered.
Issue 26: Existing regulatory mechanisms are adequate, including:
the Migratory Bird Treaty Act (MBTA); State listings for Arizona, New
Mexico, and California; section 404 of the Clean Water Act; Bureau of
Land Management and Forest Service policies; Executive Orders 11988 and
11990; protection of riparian habitat due to presence of other listed
species; private and/or cooperative management plans at local areas.
Service Response: The Service considered these regulatory
mechanisms and management plans, and determines that overall existing
regulatory mechanisms are insufficient to conserve and recover E. t.
extimus in the face of the primary threats of loss and modification of
habitat and cowbird parasitism. A full discussion of Federal and State
protection is found in this document under Factor D: ``Inadequacy of
existing regulatory mechanisms''.
The Service recognizes that some local management plans benefit and
conserve E. t. extimus and its habitat. Examples include management of
the Bureau of Land Management's San Pedro Riparian National
Conservation Area (SPRNCA) in Arizona, where six years of livestock
exclusion have resulted in significant restoration of riparian habitats
and increases in birds associated with habitats similar to E. t.
extimus (Krueper 1993). Willow [[Page 10704]] flycatchers have not yet
returned to their historical locations on the SPRNCA but may soon.
Habitat protection and cowbird management at The Nature Conservancy's
Kern River Preserve and on Marine Corps Base Camp Pendleton in
California have improved habitat and reduced brood parasitism pressures
for resident E. t. extimus (Griffith and Griffith 1993). Wetland
management at Bosque del Apache National Wildlife Refuge in New Mexico
is apparently sustaining a small population of flycatchers. While these
actions are beneficial, they provide for E. t. extimus only at several
locales. Further, long-term continuation of these management actions is
not assured.
Provisions of section 404 of the Clean Water Act do not
specifically protect E. t. extimus or its habitat, but do provide some
protection to the aquatic and riparian ecosystems of which it is a
part. Section 404 of the Clean Water Act also provides for mitigation
of destruction of these habitats, however, allowing even temporary
destruction of riparian habitat is not consistent with the immediate
conservation needs of E. t. extimus.
Issue 27: The Service did not use the best available scientific or
commercial information in making this determination; the Service
presented insufficient and inconclusive information to support listing;
the proposed rule used information which was general, incomplete, and
originated with other flycatcher subspecies; the proposed rule was
premature; the Service did not adequately solicit information and
public input; scientific, economic, biological, hydrological and
botanical data must support listing; how does the Service know the
scientific information supporting listing was right?
Service Response: The Service canvassed the published literature
regarding the taxonomy, ecology, and biology of the southwestern willow
flycatcher, and the threats to it and its habitat. Because numerous and
complex phenomena and processes were involved, this information ranged
from general (e.g., wide scale trends in riparian habitat) to very
specific (status of nesting groups). The Service believes it used the
best available information, and has determined that this information is
adequate to support listing. The Service evaluates sources before using
or discounting information. In general, the Service expects that
publications in peer-reviewed scientific journals, reports from land
and resource management agencies, and dissertations or reports from
academic or research institutions have undergone technical review.
Other information sources are considered more anecdotal, and the
Service seeks to confirm such information before using it.
Issue 28: The Service should comply with the National Environmental
Policy Act (NEPA) by completing an Environmental Impact Statement
(EIS), and comply with 40 CFR 1506 to reduce duplication between NEPA
and State and local requirements; the Service should comply with 40 CFR
1508.20 to compensate for producing substitute resources or
environments; the Service should engage in joint planning with local
governments under NEPA regulations.
Service Response: As noted in this final rule, the Service has
determined that an Environmental Assessment, as defined under the
authority of NEPA, need not be prepared for listing actions. A notice
outlining the Service's reasons for this determination was published in
the Federal Register on October 25, 1983 (48 FR 49244). Because of this
determination, an EIS also need not be prepared. Also because of this
determination, reduction of duplication between the NEPA process and
State and local agencies, and joint planning between those agencies and
the NEPA process, are rendered moot.
Issue 29: The proposed rule violates the Regulatory Flexibility
Act; no Regulatory Impact Analysis/Assessment as required under
Executive Orders 12291 and 12866 was completed; it also may be
inconsistent with the mandates of other agencies.
Service Response: Decisions on listing and reclassification under
the Act are made based on five factors defined in section 4(a)(1) of
the Act. These five factors are discussed in this rule, as they relate
to E. t. extimus. The Act requires the Service to consider only
scientific and commercial information relating to these five factors in
making listing determinations, not economic information. Economic
information is considered in designating critical habitat, which is not
part of this rule. Therefore, compliance with the Regulatory
Flexibility Act and Executive Orders 12291 and 12866 is not an issue
for this action, but will be addressed if a critical habitat
designation is made (H.R. Conf. Rep. No. 835, 97th Cong., 2d Sess. 20
(1982); accord, S. Rep. No. 418, 97th Cong., 2d Sess. 4 (1982)).
Where conservation and recovery of threatened and endangered
species is inconsistent with other mandates of Federal agencies,
processes under section 7 of the Act serve to evaluate projects arising
from those mandates, with regard to protection of listed species.
However, section 2(c) of the Act requires all Federal departments and
agencies to conserve listed species and further the purposes of the
Act.
Issue 30: The Service should complete a Takings Implications
Assessment prior to listing/designating critical habitat.
Service Response: The Service will complete a takings analysis for
any final designation of critical habitat in compliance with Executive
Order 12630 and the Attorney General's supplemental guidelines issued
June 30, 1988. In accordance with those guidelines and Interior
Department policy, this analysis will be completed after listing, not
as part of consideration of the listing determination itself.
Issue 31: Requests were received for local public hearings.
Service Response: The proposed rule stated that three public
hearings would be held. Because of many requests for additional
hearings, a total of six public hearings were held. Regulations at 50
CFR 424.16(c)(3) require the Service to hold one public hearing if
requested.
Issue 32: The time allowed for public comments was inadequate; the
proposal should have been subjected to peer review.
Service Response: The Service is required to accept public comments
for at least 60 days regarding proposals to list and/or designate
critical habitat (50 CFR 424.16(c)(2)). In this case the Service
initially announced a 90-day public comment period, then extended that
another 40 days for a total of 130 days (July 23, 1993 through November
30, 1993). Public comment periods and public hearings are the
mechanisms by which the Service receives input from all interested
parties, including scientific peer review.
Issue 33: Listing would require private property owners to consult
with the Service on their actions; listing and/or designating critical
habitat constitute take of private property rights; adverse
modification of critical habitat would be prohibited on private lands;
the Service failed to notify the affected public of the consequences of
adverse modification of critical habitat; listing and/or designating
critical habitat may affect civil rights.
Service Response: Listing does not require private property owners
to consult with the Service on actions which may affect a listed
species. However, section 7 of the Act does require Federal agencies to
consult on actions which they fund, permit, or carry out if those
actions may affect a listed species or adversely modify critical
habitat. Any potential take of private property will be analyzed in
compliance with Executive Order 12630 [[Page 10705]] (see Issue 30). As
discussed later (Issue 35), because critical habitat is not being
designated with this rule, comments regarding critical habitat will be
addressed during subsequent actions regarding critical habitat.
Issue 34: Requests were received to be on a mailing list for all
actions relating to this issue or to be provided personal notification
of a final decision.
Service Response: The Service tries to maintain mailing lists for
specific issues whenever possible. However, when large numbers of
parties request to be on such lists, it becomes logistically and
financially unfeasible to mail information to each party. This issue is
one of those, and the Service must rely to some degree on mass
communication forums like news releases, public notices in newspapers,
and publications in the Federal Register.
Issue 35: Numerous comments were received regarding critical
habitat.
Service Response: Critical habitat for E. t. extimus is not being
designated with this rule; therefore, the above issues are not
addressed here. Designation of critical habitat is being deferred while
the Service further considers the extent to which designation is
appropriate. Issues pertaining to this designation will be addressed
when a final decision is made with regard to the critical habitat
proposal.
Issue 36: Numerous comments were received regarding recovery of E.
t. extimus, including: the Service has no recovery plan for E. t.
extimus; the proposed rule failed to identify recovery goals for
habitat, flycatcher numbers, and flycatcher distribution; the proposed
rule failed to identify what actions will be used to achieve recovery;
a recovery plan should address control of cowbird parasitism, nest
damage by livestock, tamarisk eradication, wintering habitat,
monitoring populations, protection of public and private lands from
fire; cowbird parasitism cannot be addressed by listing and designating
critical habitat; cowbirds are not easily controlled without
sacrificing flycatchers and/or impacting habitat; the proposed rule
contained no livestock managing strategy; rotating livestock will allow
habitat enhancement/recovery; the factors affecting riparian habitats
are numerous and complex; failure to address all could be futile or
have damaging effects.
Service Response: Section 4(f) of the Act authorizes the Service to
develop and implement recovery plans for listed species, not species
that are proposed for listing. For E. t. extimus, this process
therefore begins with the effective date of listing. In accordance with
section 4(f)(B) of the Act the recovery plan process will address
actions necessary to achieve conservation and recovery of E. t.
extimus, will identify measurable criteria by which recovery (i.e., the
point at which protection under the Act is no longer necessary) can be
gauged, and will identify the time and costs required to achieve
recovery. The specific issues identified above will be considered in
developing a recovery plan, and that plan will be available for public
review and comment prior to adoption. Monitoring species is frequently
an element of recovery plans, and is also required by section 4(g) of
the Act for any species deemed to be recovered.
Issue 37: Several commenters questioned the motivations of the
petitioners in requesting the listing, and others apparently believed
the petitioners authored the listing proposal. Several commenters noted
that the petition contained inaccuracies, and therefore no listing
proposal should have resulted.
Service Response: The Service cannot speak for the petitioners'
motivations in requesting listing of E. t. extimus. The Service judged
the petition solely on the scientific information it contained.
Inaccuracies were found in the petition, but on the whole the Service
determined that it presented substantial information indicating that
listing may be warranted. The listing proposal was authored by the
Service, not the petitioners. The Service developed its proposal not
from the petition, but from information gained from journal
publications, agency reports, and the general public's responses to
several information solicitations. This status review process had
resulted in the Service designating E. t. extimus a category 1
candidate species prior to the petition being received. That
designation indicated that the Service had sufficient information to
support a listing proposal but did not publish a proposal immediately
because it was dealing with listing actions of higher priority.
Information presented by the petitioners that the Service did not
already possess was checked for accuracy; information that could not be
confirmed, or was found to be inaccurate, was not used.
Issue 38: The Service is required to purchase interest in land or
water for implementation of the Act; this violates the U.S.
Constitution.
Service Response: Section 5 of the Act directs the Secretary to use
land acquisition and other authorities of the Fish and Wildlife Act of
1956, as amended, the Fish and Wildlife Coordination Act, as amended,
and the Migratory Bird Conservation Act, as appropriate. The Secretary
is authorized, but not required, to acquire interest in land or water
to conserve threatened and endangered species. The Service does not
carry out these authorities in violation of the U.S. Constitution. The
Service does not acquire all lands designated as critical habitat for a
listed species, and does not develop critical habitat designations
based on land ownership or interest of landowners in purchasing or
selling properties. It is the Service's policy to acquire property only
on a voluntary basis from willing sellers.
Issue 39: Land use outside occupied/critical habitat will be
adversely impacted.
Service Response: Federal actions that take place outside occupied
habitat or critical habitat, but that may affect E. t. extimus, will be
subject to consultation between the action agency and the Service in
accordance with section 7 of the Act. Exclusively private actions are
unaffected by listing and/or designation of critical habitat, provided
they do not result in violation of section 9 of the Act (e.g., take of
the species).
Issue 40: Listing (regardless of critical habitat) will have
adverse impacts on local economy; economic impacts of listing were not
addressed; the Act requires the Service to consider impacts on other
wildlife species and social and economic impacts prior to listing.
Service Response: Consideration of economic effects is required for
designation of critical habitat. The Act requires that species listing
decisions be based solely on the best scientific and commercial
information available, which precludes consideration of social or
cultural impacts or impacts on other species. (See section 4(b)(1)(A)
of the Act). The Service anticipates no significant impacts on other
native wildlife species as a result of listing, with the probable
exception of the brown-headed cowbird.
Issue 41: Who initiated, performed, and paid for studies along the
Kern River?
Service Response: Reports on studies done on the Kern River were
published by Harris et al. (1986), Harris et al. (1987), Whitfield
(1990), and Harris (1991). Specific information on project
participants, funding sources, and cooperators can be found in those
sources. The Service understands that monitoring and cowbird control
are being continued by the Kern River Research Center and The Nature
Conservancy, with funding assistance from the State of California and
the Service. [[Page 10706]]
Issue 42: The Service should perform additional surveys before
listing.
Service Response: The Service is supporting continuing surveys to
detect additional E. t. extimus, to monitor known nest sites, and to
evaluate habitat presence, quality, and distribution. The Service
supports these surveys with funding to States in accordance with
section 6 of the Act, and through logistical and technical assistance
to other agencies and parties. Extensive surveys in New Mexico and
Arizona in 1993 located E. t. extimus in numbers that do not
significantly change the total population estimates made in the
proposed rule. These surveys also confirmed high levels of brood
parasitism by cowbirds. With low estimates of total flycatcher numbers
being validated by continuing surveys, the Service has determined that
sufficient information exists on the threats of habitat loss and
cowbird parasitism to justify listing.
Issue 43: The Service failed to consult adequately with private
interests, State, Federal, and local agencies prior to publishing the
proposed rule.
Service Response: The Service published public requests for
information on the status of E. t. extimus in the Federal Register when
it was designated a category 2 candidate species in January 1989, and
when it was designated a category 1 species in November 1991. The
Service supplemented these requests with general mailings soliciting
information, and information solicitations in professional
publications. Beyond these mechanisms, the Service is constrained by
funding limitations and citizens' suits such as Environmental Defense
Center, Inc. vs. Babbitt et al. IV 93-1848-R (C.D. Calif.), which was
brought to compel the Service to propose listing and designation of
critical habitat for the species, that preclude individually contacting
every interested party.
Issue 44: The parties who petitioned for listing should pay for
studies supporting their request.
Service Response: Regulations implementing section 4 of the Act,
specifically the petition process [50 CFR 424.14], do not require
petitioners to fund studies supporting their request. Listing
determinations are made if existing information is deemed sufficient to
make a determination. This information typically originates from a
variety of sources.
Issue 45: The southwestern willow flycatcher is abundant. There is
no need to list.
Service Response: The Service has determined that E. t. extimus is
rare, not abundant, faces serious threats to its continued existence,
and warrants listing as endangered. See discussion under Factor A: The
present or threatened destruction, modification, or curtailment of its
habitat or range.
Issue 46: The ``little'' willow flycatcher (E. t. brewsteri) is the
most common subspecies observed and collected in the Southwest.
Service Response: The abundance of collections of E. t. brewsteri
from within the breeding range of E. t. extimus is because E. t.
brewsteri migrates through the Southwest between its Pacific coastal
breeding range and wintering grounds in Central America. E. t.
brewsteri passes through riparian habitats in the breeding range of E.
t. extimus in spring and fall, but does not breed there.
Issue 47: There is no need to list E. t. extimus in areas where it
is doing well.
Service Response: The Service has determined that E. t. extimus is
endangered; local areas where the bird is relatively stable could only
be excluded from listing or classified as threatened if they
constituted distinct population segments [50 CFR 424.02(k)]. The
Service has not identified any distinct population segments of E. t.
extimus. Further, because the Service determines E. t. extimus to be
endangered, all existing habitat and local nesting concentrations are
deemed to be essential to the conservation and recovery of the species.
Protection of locales where the bird is doing relatively well may be
especially important for the conservation and recovery of E. t.
extimus.
Issue 48: Prey availability may be a limiting factor.
Service Response: The Service recognizes that food availability is
always a potential limiting factor in wildlife populations. It is
possible that reduction of riparian habitats not only reduced
vegetation for nesting, but reduced or altered the arthropod fauna
associated with surface water and extensive vegetation. Also, as noted
in this rule, some speculation exists that tamarisk provides a
substandard nesting habitat because it supports a significantly
different insect fauna than native vegetation. However, no information
was available to evaluate this factor directly for E. t. extimus.
Issue 49: Several comments were received that pertained to the
Service's management of the 90-day petition finding, including that the
90-day petition finding was late; that it is not the Service's role to
conduct a status review if information in a petition is lacking; and
that a 30-day comment period on the 90-day petition finding was
insufficient.
Service Response: The Service acknowledges that its finding on the
listing petition was published after 90 days, however, the Act (section
4(b)(3)(A) states that the [Service] shall, to the maximum extent
practicable, make a petition finding within 90 days (emphasis added).
Because the petition was found to present substantial information
indicating that the petitioned action may have been warranted, the
Service continued a status review after this finding, in accordance
with 50 CFR 424.14(b)(3). There are no requirements for the Service to
open a formal comment period regarding a 90-day petition finding. The
Service did so in this case to solicit additional information on E. t.
extimus. In reaching its 12-month petition finding, the Service
considered all information received within the 30-day period
identified, and information received for several months thereafter.
Issue 50: E. t. extimus should be listed as threatened, not
endangered.
Service Response: The Service carefully evaluated the status of E.
t. extimus and has determined that it meets the definition of an
endangered species, not a threatened species. As stated in the proposed
rule, (58 FR 39495) threatened status would not be appropriate because
the large historic habitat loss already has caused extirpation
throughout a significant portion of the species' range. Population
numbers are extremely low, and a variety of threats are serious and
imminent.
Issue 51: Restrictions on rural livestock grazing will cause
ranching to become nonviable, and the land will be converted by
suburban development, which is a greater threat to E. t. extimus than
overgrazing.
Service Response: The conversion of lands from livestock grazing to
suburban development is hypothetical and therefore cannot drive the
Service's determination on this issue. Much of the livestock grazing
that may be affected by this rule takes place on Federal lands.
Therefore, conversion to suburban development would require land
exchanges or sales. These actions, if they were determined to affect E.
t. extimus, would require consultation under section 7 of the Act.
Regardless, prioritization of threats should be undertaken in the
recovery, rather than listing, process.
Issue 52: The proposed rule fails to consider changing ecological
factors: drought, migration patterns, nesting habits, and climatic
changes. [[Page 10707]]
Service Response: The Service recognizes that populations of E. t.
extimus are likely to fluctuate naturally in response to various
ecological factors. However, the Service believes that declines in
habitat availability and increased exposure to cowbird parasitism have
caused population reductions beyond the scale of natural fluctuations.
Fluctuations in response to nonanthropogenic phenomena are likely to
continue, but the current population levels are so low that these
natural phenomena may be sufficient to cause local extirpations.
Issue 53: Restrictions associated with listing would be in conflict
with Kern County's General Plan.
Service Response: Under section 4 of the Act, the Service considers
only scientific and commercial information relating to the five listing
factors outlined in section 4(a)(1) and discussed with respect to E. t.
extimus in this rule. Therefore, conflicts with local plans were not
considered in making this determination. However, the Service strives
to pursue conservation and recovery of listed species in cooperation
with State and local authorities, and seeks to minimize conflicts.
Issue 54: Listing and critical habitat designations will adversely
affect flood control measures, some authorized by the Federal Emergency
Management Agency and other Federal and State regulations; the proposed
rule failed to consider flood accommodation needs, channelization, and
clearing vegetation.
Service Response: Flood control measures virtually always involve a
Federal agency, through funding, permitting, and/or other action.
Therefore, flood control measures that may affect E. t. extimus would
undergo consultation under section 7 of the Act. Section 7 and its
implementing regulations have provisions for emergency consultations,
and for actions within presidentially declared disaster areas.
Issue 55: Government agencies are responsible for many impacts to
riparian areas; campgrounds, fish hatcheries, and some district offices
are located in riparian areas.
Service Response: The Service acknowledges that some Federal
actions are in part responsible for the threats facing E. t. extimus.
As a result of listing, those Federal actions will be subject to
consultation under section 7 of the Act to evaluate and minimize the
effects of those actions.
Issue 56: The Service does not acknowledge receipt of comments on
listing, and probably does not read them.
Service Response: The Service does not routinely acknowledge
receipt of each letter commenting on listing proposals. The number of
letters in this case made it logistically and financially impossible to
acknowledge each one. However, all letters were read, and their issues
addressed either here or elsewhere in this final rule. All comment
letters and transcripts of public hearings are retained in the
permanent file on this species and are available for public inspection.
Issue 57: Protecting flycatcher habitat may restrict mosquito
control, which is important for control of encephalitis and other
mosquito-borne diseases.
Service Response: Where such control involves a Federal action,
mosquito and disease control actions may be subject to consultation
under section 7(a)(2) of the Act, which would evaluate but not
necessarily restrict or significantly modify the project. Ultimately,
section 7(e) of the Act allows exemptions to the requirements of
section 7(a)(2).
Summary of Factors Affecting the Species

After a thorough review and consideration of all information
available, the Service has determined that the southwestern willow
flycatcher should be classified as an endangered species. Procedures
found at section 4(a)(1) of the Act and regulations implementing the
listing provisions of the Act (50 CFR Part 424) were followed. A
species may be determined to be an endangered or threatened species due
to one or more of the five factors described in section 4(a)(1). These
factors and their application to the southwestern willow flycatcher
(Empidonax traillii extimus) are as follows:

A. The Present or Threatened Destruction, Modification, or Curtailment
of its Habitat or Range

Large scale losses of southwestern wetlands have occurred,
particularly the cottonwood-willow riparian habitats of the
southwestern willow flycatcher (Phillips et al. 1964, Carothers 1977,
Rea 1983, Johnson and Haight 1984, Katibah 1984, Johnson et al. 1987,
Unitt 1987, General Accounting Office (GAO) 1988, Bowler 1989, Szaro
1989, Dahl 1990, State of Arizona 1990, Howe and Knopf 1991). Changes
in riparian plant communities have resulted in the reduction,
degradation, and elimination of nesting habitat for the willow
flycatcher, curtailing the ranges, distributions, and numbers of
western subspecies, including E. t. extimus (Gaines 1974, Serena 1982,
Cannon and Knopf 1984, Klebenow and Oakleaf 1984, Taylor 1986, Unitt
1987, Schlorff 1990, Ehrlich et al. 1992).
Dahl (1990) reviewed estimated losses of wetlands between 1780 and
the 1980's in the Southwest: California is estimated to have lost 91
percent, Nevada 52 percent, Utah 30 percent, Arizona 36 percent, New
Mexico 33 percent, and Texas 52 percent. As much as 90 percent of major
lowland riparian habitat has been lost or modified in Arizona (State of
Arizona 1990). Franzreb (1987) noted that ``[B]ottomland riparian
forests are the most highly modified of natural landscapes in
California.''
Loss and modification of southwestern riparian habitats have
occurred from urban and agricultural development, water diversion and
impoundment, channelization, livestock grazing, off-road vehicle and
other recreational uses, and hydrological changes resulting from these
and other land uses. Rosenberg et al. (1991) noted that ``it is the
cottonwood-willow plant community that has declined most with modern
river management.'' Loss of the cottonwood-willow riparian forests has
had widespread impact on the distribution and abundance of bird species
associated with that forest type (Hunter et al. 1987, Hunter et al.
1988, Rosenberg et al. 1991).
Overuse by livestock has been a major factor in the degradation and
modification of riparian habitats in the western United States. These
effects include changes in plant community structure and species
composition, and relative abundance of species and plant density. These
changes are often linked to more widespread changes in watershed
hydrology (Rea 1983, General Accounting Office 1988) and directly
affect the habitat characteristics critical to E. t. extimus. Livestock
grazing in riparian habitats typically results in reduction of plant
species diversity and density, especially of palatable broadleaf plants
like willows and cottonwood saplings, and is one of the most common
causes of riparian degradation (Carothers 1977, USDA Forest Service
1979, Rickard and Cushing 1982, Cannon and Knopf 1984, Klebenow and
Oakleaf 1984, GAO 1988, Clary and Webster 1989, Schultz and Leininger
1990).
Increases in abundance of riparian bird species have followed
reduction, modification, or removal of cattle grazing. Krueper (1993)
found the following increases in birds associated with cottonwood-
willow habitat on Arizona's San Pedro River four years after the
removal of livestock: yellow warbler, 606 percent; common yellow-
throat, 2,128 percent; yellow-breasted [[Page 10708]] chat, 423
percent. Bock et al. (1993) found that 40 percent of the riparian bird
species they examined, including the willow flycatcher (various
subspecies), were negatively affected by livestock grazing. Increases
in willow flycatcher numbers (various subspecies) have followed
reduction, modification, or removal of cattle grazing. Taylor (1986)
found a negative correlation between recent cattle grazing and
abundance of numerous riparian birds, including the Great Basin willow
flycatcher (E. t. adastus). In an area ungrazed since 1940, his bird
counts were five to seven times higher than comparable plots where
grazing was terminated in 1980. Taylor and Littlefield (1986) found
higher numbers of Great Basin willow flycatchers correlated with
minimal or nonexistent livestock grazing. Klebenow and Oakleaf (1984)
listed the Great Basin willow flycatcher among bird species that
declined from abundant to absent in riparian habitats degraded in part
by overgrazing. Schlorff reported willow flycatchers returning to Modoc
County, California, several years after removal of livestock grazing
(pers. comm. cited in Valentine et al. 1988). Knopf et al. (1988) found
that, during the summer, Great Basin willow flycatchers were present on
winter-grazed pastures, but were virtually absent from summer-grazed
pastures.
The Service believes that documentation of livestock impacts on
other willow flycatcher subspecies is relevant to E. t. extimus,
because linear riparian habitats in the arid range of E. t. extimus are
especially vulnerable to fragmentation and destruction by livestock. As
shady, cool, wet areas providing abundant forage, they are
disproportionately preferred by livestock over the surrounding xeric
uplands (Ames 1977, Valentine et al. 1988, A. Johnson 1989). Harris et
al. (1987) believed that termination of grazing along portions of the
South Fork of the Kern River in California was responsible for
increases in riparian vegetation and, consequently, nesting E. t.
extimus. Suckling et al. (1992) noted that most of the areas still
known to support E. t. extimus have low or nonexistent levels of
livestock grazing. More recent surveys (Muiznieks et al. 1994) have
found E. t. extimus in areas with livestock grazing; however, these
occur in widely dispersed, small groups whose nesting success is
largely unknown, and where livestock grazing intensity and seasonality
are also unknown.
Another likely factor in the loss and modification of southwestern
willow flycatcher habitat is invasion by the exotic tamarisk. Tamarisk
(also called saltcedar) was introduced into western North America from
the Middle East in the late 1800's as an ornamental windbreak and for
erosion control. It has spread rapidly along southwestern watercourses,
typically at the expense of native riparian vegetation, especially
cottonwood/willow communities. Although tamarisk is present in nearly
every southwestern riparian community, its dominance varies. It has
replaced some communities entirely, but occurs at a low frequency in
others.
The spread and persistence of tamarisk has resulted in significant
changes in riparian plant communities. In monotypic tamarisk stands,
the most striking change is the loss of community structure. The
multilayered community of herbaceous understory, small shrubs, middle-
layer willows, and overstory deciduous trees is often replaced by one
monotonous layer. Plant species diversity has declined in many areas,
and relative species abundance has shifted in others. Other effects
include changes in percent cover, total biomass, fire cycles, thermal
regimes, and perhaps insect fauna (Kerpez and Smith 1987, Carothers and
Brown 1991, Rosenberg et al. 1991, Busch and Smith 1993).
Disturbance regimes imposed by man (e.g., grazing, water diversion,
flood control, woodcutting, and vegetation clearing) have facilitated
the spread of tamarisk (Behle and Higgins 1959, Kerpez and Smith 1987,
Hunter et al. 1988, Rosenberg et al. 1991). Cattle find tamarisk
unpalatable. However, they eat the shoots and seedlings of cottonwood
and willow, acting as a selective agent to shift the relative abundance
of these species (Kerpez and Smith 1987). Degradation and, in some
cases, loss of native riparian vegetation lowered the water table and
resulted in the loss of perennial flows in some streams. With its deep
root system and adaptive reproductive strategy, tamarisk thrives or
persists where surface flow has been reduced or lost. Further, tamarisk
establishment often results in a self-perpetuating regime of periodic
fires, which were uncommon in native riparian woodlands (Busch and
Smith 1993).
Manipulation of perennial rivers and streams has resulted in
habitats that tend to allow tamarisk to outcompete native vegetation.
Construction of dams created impoundments that destroyed native
riparian communities. Dams also eliminated or changed flood regimes,
which were essential in maintaining native riparian ecosystems.
Changing (usually eliminating) flood regimes provided a competitive
edge to tamarisk. In contrast to native phreatophytes, tamarisk does
not need floods and is intolerant of submersion when young. Diversion
of water caused the lowering of near-surface groundwater and reduced
the relative success of native species in becoming established.
Irrigation water containing high levels of dissolved salts also favors
tamarisk, which is more tolerant of high salt levels than most native
species (Kerpez and Smith 1987, Busch and Smith 1993).
The rapid spread of tamarisk has coincided with the decline of the
southwestern willow flycatcher. Although E. t. extimus has been
documented nesting in tamarisk, it is not known whether, over the long
term, reproductive success of southwestern willow flycatchers nesting
in tamarisk has differed from the success of flycatchers nesting in
native vegetation. Studies in Arizona have documented low breeding
densities and low reproductive success for southwestern willow
flycatchers nesting in tamarisk (Hunter et al. 1988, Muiznieks et al.
1994). These data, coupled with a possible decrease in the arthropod
prey base and thermal protection for nests provided by tamarisk,
suggest that tamarisk may provide poor quality nesting habitat.
However, more extensive comparative studies are needed to determine the
overall impact on the southwestern willow flycatcher of the conversion
of native broadleaf-dominated riparian habitat to tamarisk-dominated
habitat.
Other studies of riparian bird communities have documented changes
in bird species diversity, corresponding with invasion by tamarisk.
Conversion to tamarisk typically coincides with reduction or
complete loss of bird species strongly associated with cottonwood-
willow habitats. These include the yellow-billed cuckoo (Coccyzus
americanus), summer tanager (Piranga rubra), northern oriole (Icterus
galbula), and the southwestern willow flycatcher (Hunter et al. 1987,
Hunter et al. 1988, Rosenberg et al. 1991). While Brown and Trosset
(1989) believed tamarisk may serve as an ``ecological equivalent'' to
native vegetation, they noted that their study occurred where a
tamarisk community became established where no native equivalent
existed before.
Some authors believe tamarisk may not provide the thermal
protection that native broadleaf species do (Hunter et al. 1987, Hunter
et al. 1988). This could be important at lower elevations in the
Southwest, where extreme high temperatures are common during the bird's
midsummer breeding season. It is [[Page 10709]] also possible that
tamarisk affects E. t. extimus by altering the riparian insect fauna
(Carothers and Brown 1991). Some sources also speculated that nests in
tamarisk stands may be more easily located by brown-headed cowbirds
(see cowbird discussion below). Hunter et al. (1987) reported the
willow flycatcher as one of seven midsummer-breeding builders of open
nests that were found in tamarisk at higher elevations but not lower
elevations. Nesting E. t. extimus have been found in tamarisk at middle
elevations (610-1200 m (2000-3500 feet)) (Hundertmark 1978, Hubbard
1987, Hunter et al. 1987, Brown 1988, Sogge et al. 1993, Muiznieks et
al. 1994). However, nest success in tamarisk at these elevations
appears to be low (Sogge and Tibbitts 1992, Sogge et al. 1993,
Muiznieks et al. 1994). The species is essentially absent from
tamarisk-dominated habitats below 610 m (2000 feet). On the lower
Colorado River (approximately 25 m (80 feet)) where tamarisk is widely
dominant, the only territories found in recent decades were in relict
stands dominated by willow, cottonwood, and other native vegetation
(Muiznieks et al. 1994). Unitt (1987) speculated that at higher
elevations and in the eastern portion of its range, some E. t. extimus
populations may be adapting to tamarisk.
Water developments also likely reduced and modified southwestern
willow flycatcher habitat. The series of dams along most major
southwestern rivers (Colorado, Gila, Salt, Verde, Rio Grande, Kern, San
Diegito, and Mojave) have altered riparian habitats downstream of dams
through hydrological changes, vegetational changes, and inundated
habitats upstream. New habitat is sometimes created along the shoreline
of reservoirs, but this habitat (often tamarisk) is often unstable
because of fluctuating levels of regulated reservoirs (Grinnell 1914,
Phillips et al. 1964, Rosenberg et al. 1991). Construction of Glen
Canyon Dam on the Colorado River allowed establishment of a tamarisk
riparian community downstream in the Grand Canyon, where a small
population of E. t. extimus exists, with poor reproduction (Brown 1991,
Sogge et al. 1993). However, Lake Powell, formed upstream of the dam,
inundated what was apparently superior habitat, with E. t. extimus
considered common (Behle and Higgins 1959).
Diversion and channelization of natural watercourses are also
likely to have reduced E. t. extimus habitat. Diversion results in
diminished surface flows and increased salinity of residual flows.
Consequent reductions and composition changes in riparian vegetation
are likely. Channelization often alters stream banks and fluvial
dynamics necessary to maintain native riparian vegetation.
Suckling et al. (1992) suggested that logging in the upper
watersheds of southwestern rivers may constitute another potential
threat to the southwestern willow flycatcher. They stated that logging
increases the likelihood of damaging floods in southwestern willow
flycatcher nesting habitat.
Finally, the willow flycatcher (all subspecies) is listed among
neotropical migratory birds that may be impacted by alteration of
wintering habitat, as through tropical deforestation (Finch 1991,
Sherry and Holmes 1993).

Population Trends for Each State Are Discussed Briefly Below

California. All three resident subspecies of the willow flycatcher
(E. t. extimus, E. t. brewsteri, and E. t. adastus) were once
considered widely distributed and common in California, wherever
suitable habitat existed (Wheelock 1912, Willett 1912, Grinnell and
Miller 1944). The historic range of E. t. extimus in California
apparently included all lowland riparian areas of the southern third of
the State. Unitt (1984, 1987) concluded that it was once fairly common
in the Los Angeles basin, the San Bernardino/Riverside area, and San
Diego County. Willett (1912, 1933) considered the bird to be a common
breeder in coastal southern California. Nest and egg collections
indicate the bird was a common breeder along the lower Colorado River
near Yuma in 1902 (T. Huels, University of Arizona in litt.,
transcripts of H. Brown's field notes).
All three willow flycatcher subspecies breeding in California have
declined, with declines most critical in E. t. extimus, which remains
only in small, disjunct nesting groups (Unitt 1984 and 1987, Gaines
1988, Schlorff 1990, Service unpubl. data). Only two nesting groups
have been stable or increasing in recent years. One is on private land
where habitat impacts from livestock grazing have been virtually
eliminated (Harris et al. 1987, Whitfield 1990). This group on the
South Fork of the Kern River experienced numerical declines in 1991 and
1992, but increases in nesting success were realized in 1992 and 1993,
attributed to shaking (killing) or removing cowbird eggs or nestlings
found in flycatcher nests, and trapping cowbirds (Whitfield and Laymon,
Kern River Research Center, in litt. 1993). The other apparently stable
nesting group is along the Santa Margarita River on Marine Corps Base
Camp Pendleton, where cowbird numbers have also been reduced by
trapping (Griffith and Griffith 1993). Approximately eight other
nesting groups are known in southern California, all of which consisted
of six or fewer nesting pairs in recent years (Unitt 1987, Schlorff
1990, Service, unpubl. data). Using the most recent information for all
areas, approximately 70 pairs and 8 single southwestern willow
flycatchers are known to exist in California. Where information on
population trends since the mid-1980's is available, most areas show
declines. Three recent status reviews considered extirpation from
California to be possible, even likely, in the foreseeable future
(Garrett and Dunn 1981, Harris et al. 1986, Schlorff 1990). The State
of California classifies the willow flycatcher as endangered
[California Department of Fish and Game (CDFG) 1992].
Arizona. Records indicate that the former range of the southwestern
willow flycatcher in Arizona included portions of all major watersheds
(Colorado, Salt, Verde, Gila, Santa Cruz, and San Pedro). Historical
records exist from the Colorado River near Lee's Ferry and near the
Little Colorado River confluence (Phillips, pers. comm., cited in Unitt
1987), and along the Arizona-California border (Phillips 1948, Unitt
1987), the Santa Cruz River near Tucson (Swarth 1914, Phillips 1948),
the Verde River at Camp Verde (Phillips 1948), the Gila River at Fort
Thomas (W.C. Hunter, pers. comm., cited in Unitt 1987), the White River
at Whiteriver, the upper and lower San Pedro River (Willard 1912,
Phillips 1948), and the Little Colorado River headwaters area (Phillips
1948).
The southwestern willow flycatcher has declined throughout Arizona.
The subspecies was apparently abundant on the lower Colorado River in
1902 (T. Huels in litt., transcripts of H. Brown's field notes), but
only four to five territories were located in 1993 (Muiznieks et al.
1994). Elsewhere in the State, E. t. extimus persists only in several
small, widely scattered locations. In the Grand Canyon, several groups
of nesting birds have fluctuated from a high of 11 singing males in
1986 (Brown 1988) to two pairs and three single birds in 1992 (Sogge
and Tibbitts 1992). Grand Canyon surveys in 1993 located 13 birds; six
unpaired individuals, two pairs, and what appeared to be one male with
two females. No nesting attempts were successful (Sogge et al. 1993).
Although Brown (et al. 1987) noted E. t. extimus as nesting in Havasu
Canyon, in 1993 none were located there and cowbirds were abundant
(Sogge et al. 1993). A [[Page 10710]] location on the lower San Pedro
River apparently supported relatively large numbers of E. t. extimus in
the 1940's (G. Monson, private individual, in litt. 1993 and pers.
comm. 1993), but only a single pair in 1978 and 1979, and none in 1986
(Unitt 1987). Following habitat improvements at this locale, six to
seven singing males were present in 1993, and a total of 11 singing
males were located at two other locations on the lower San Pedro in
1993 (Muiznieks et al. 1994).
Historically occupied habitat on the upper San Pedro River is in
the process of rehabilitation, but remains unoccupied by nesting E. t.
extimus (Krueper and Corman 1988, D. Krueper unpubl. data). Two small
groups at high elevations in the White Mountains, comprising
approximately five singing males each, have remained relatively stable
numerically from 1985 to 1993 (Muiznieks et al. 1994, Arizona Game and
Fish Department (AGFD), unpubl. data). At a site on the Verde River in
central Arizona where R. Ohmart (unpubl. data) observed four nesting
pairs in 1992, one pair and one single male were present in 1993. The
single nest produced only a cowbird young. Of 13 river reaches in
Arizona studied by Hunter et al. (1987), nesting E. t. extimus were
extirpated from eight, declining in two, and present in stable numbers
in three.
Statewide surveys in 1993 located between 42 and 56 territorial
males, and all nest sites were considered vulnerable to habitat loss
and cowbird parasitism (Muiznieks et al. 1994). Preliminary data from
1994 surveys indicate that approximately 70 to 80 breeding pairs were
found at a total of 12 locations in the State. This included the
discovery of a group of flycatchers at one location consisting of
approximately 15 breeding pairs. Brood parasitism by cowbirds was
documented at at least six (50%) of those 12 sites. Brown-headed
cowbirds were documented at all 12 breeding locations (Arizona Game and
Fish Department, in prep.).
Where information on population trends since the mid-1980's is
available, most areas show declines and/or high rates of cowbird
parasitism. In early 1993, catastrophic flooding on the Verde, Gila,
and San Pedro Rivers temporarily damaged many sites inhabited since the
mid-1980's, and much potential habitat. Unitt (1987) concluded that
``Probably the steepest decline in the population levels of E. t.
extimus has occurred in Arizona * * * E. t. extimus has been extirpated
from much of the area from which it was originally described, the
riparian woodlands of southern Arizona.'' The State of Arizona
classifies the willow flycatcher as endangered (AGFD 1988).
New Mexico. Bailey (1928) classified breeding willow flycatchers in
New Mexico as E. t. brewsteri, according to Oberholser's (1918)
taxonomy of that time. Because of few records at that time, she
believed that either the bird was rare or was overlooked by most
observers and collectors. More recently, Hubbard (1987) reviewed and
summarized the flycatcher's status in New Mexico. He classified
breeding birds in the State as E. t. extimus and reported breeding
locations that were generally confined to the regions west of the Rio
Grande, with records from the Rio Grande, Chama, Zuni, San Francisco,
and Gila drainages (See also Hubbard 1982). However, he provisionally
assigned all willow flycatchers nesting in New Mexico to E. t. extimus,
noting records from the Pecos River and Penasco Creek in the southeast
and from near Las Vegas in the northeast.
Both Hubbard (1987) and Unitt (1987) believed that the overall
range of E. t. extimus had not been reduced in New Mexico, but that
habitat and numbers had declined. Unitt (1987) believed the majority of
all remaining nesting birds may occur in New Mexico. Areas with 19 and
53 singing flycatchers, not distinguished as nesting or migrants, were
found on the upper Gila River (Montgomery et al. 1985, cited in
Suckling et al. 1992). Preliminary data from 1994 surveys indicate that
this breeding group is still present. However, the breeding status of
flycatchers and trend over time have not been determined (S.O.
Williams, New Mexico Department of Game and Fish--pers. comm.)
Hubbard (1987) noted that data were lacking for trends of most
nesting areas. However, where data were available, they indicated loss
of a group of 15 breeding pairs by the rising waters of Elephant Butte
Reservoir. The willow flycatcher was considered fairly common in this
area on the middle Rio Grande in the late 1970's (Hundertmark 1978).
Hubbard hypothesized that some of these birds could have moved
upstream, to new shoreline habitat created by the impoundment. Between
1987 and 1990, bird surveys along the Rio Grande Valley State Park in
Albuquerque found a single singing willow flycatcher during the
breeding season (Hoffman 1990). Current trends in New Mexico are not
being extensively monitored. However, in 1992, 71 transects along the
Rio Grande were surveyed for breeding birds, but not specifically
targeting willow flycatcher habitat. A single willow flycatcher was
located near Espanola (Leal, Meyer and Thompson, unpubl. data). In
1993, surveys of 52 locations found 31 pairs or singing males at 15 of
those locations (S.O. Williams III, New Mexico Department of Game and
Fish (NMDGF), in litt. 1993). Hubbard (1987) estimated that the State
population may total 100 pairs; that estimate has not been revised.
Hubbard (1987) found that ``the conclusion is virtually inescapable * *
* a decrease has occurred in the population of breeding willow
flycatchers in New Mexico over historic time,'' resulting from habitat
loss. The State of New Mexico classifies the willow flycatcher as
endangered (NMDGF 1988).
Texas. The eastern limit of the southwestern willow flycatcher's
breeding range is in western Texas (Unitt 1987). Collections have been
made at Fort Hancock on the Rio Grande (Phillips 1948), in the
Guadalupe Mountains (Phillips, pers. comm., cited in Unitt 1987), the
Davis Mountains (Oberholser 1974), and from unspecified locales in
Brewster County (Wolfe 1956). Wauer (1973 and 1985) considered E. t.
extimus a rare summer resident in Big Bend National Park. Data are
lacking on current population levels and trends in Texas. Loss and
modification of habitat may have reduced populations on the Rio Grande
and Pecos Rivers.
Utah. The north-central limit of breeding southwestern willow
flycatchers is in southern Utah. Behle (1985) and Unitt (1987) believed
a clinal gradation between E. t. extimus and E. t. adastus existed, but
Browning (1993) disagreed, identifying a range boundary at
approximately the 38th north parallel. Southern Utah is characterized
by extreme topographic relief. In this region, subspecific separation
may be a function of elevation, with E. t. extimus at lower elevations
(e.g., Virgin and Colorado Rivers) and E. t. adastus higher (e.g.,
Sevier River, wet meadows of mountains and high plateaus). Records that
are likely to represent E. t. extimus are from the Virgin River
(Phillips 1948, Wauer and Carter 1965, Whitmore 1975), Kanab Creek, and
along the San Juan and Colorado Rivers (Behle et al. 1958, cited in
Unitt 1987; Behle and Higgins 1959, Behle 1985; see also Browning
1993). Other reports document the subspecies being present along the
Virgin, Colorado, San Juan, and perhaps Paria Rivers (BLM, unpubl.
data). Although Behle believed E. t. extimus was always rare in
southern Utah overall (pers. comm. cited in Unitt 1987), he considered
it a locally common breeding resident where habitat existed along the
Colorado River [[Page 10711]] and its tributaries in southeastern Utah
(Behle and Higgins 1959).
Few data are available on population trends in southern Utah.
However, loss and modification of habitat is likely to have reduced
populations on the Virgin, Colorado, and San Juan Rivers. These losses
have been due to suburban expansion and habitat changes along the
Virgin River, inundation by Lake Powell on the Colorado and San Juan
Rivers, and encroachment of tamarisk throughout the region (Unitt 1987,
BLM unpublished data).
Nevada. Unitt (1987) reported only three records for Nevada, all
made before 1962. Unitt (1987), Hubbard (1987), and Browning (1993) all
considered southern Nevada (approximately south of 38 deg. north
parallel) to be within the range of E. t. extimus. However, no recent
data are available on population levels or trends. Habitat may remain
along the lower Virgin River and at the inflow of the Virgin River into
Lake Mead. However, loss and modification of habitat is likely to have
reduced populations on the Virgin and Colorado Rivers.
Colorado. Whether or not the southwestern willow flycatcher breeds
in Colorado is unclear. Hubbard (1987) believed the subspecies ranged
into extreme southwestern Colorado, Browning (1993) was noncommittal,
and Unitt (1987) tentatively used the New Mexico-Colorado border as the
boundary between E. t. extimus and E. t. adastus. Several specimens
taken in late summer have been identified as E. t. extimus, but nesting
was not confirmed (Bailey and Niedrach 1965). Phillips (1948) cautioned
that willow flycatchers in this region displayed considerable
individual variation a

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A95-4531. Public record. Not legal advice.