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<br />The southwestern willow flycatcher was proposed for listing as endangered, with critical habitat.
<br />on July 23,1993 (U.S. Fish and Wildlife Service 1993). A February 27, 1995, final rule listing
<br />the southwestern willow flycatcher as endangered became effective on March 29, 1995 (U.S.
<br />Fish and Wildlife Service 1995a). The States of Arizona, California, and New Mexico also list
<br />the southwestern willow flycatcher as endangered (Arizona Game and Fish Department 1988.
<br />California Department of Fish and Game 1992, New Mexico Department of Game and Fish
<br />1988). Following the review of comments received during the public comment period, the
<br />Service deferred the designation of critical habitat, invoking an extension on this decision until
<br />July 23, 1995. A moratorium on listing actions under the Act passed by Congress in April 1995
<br />required th~ Service to cease work on the designation of critical habitat until the moratorium is
<br />lifted.
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<br />Recent surveys have documented breeding populations of southwestern willow flycatchers in
<br />three states (California, Arizona, and New Mexico). Small numbers of probable breeders have
<br />been documented in Utah and Colorado, however breeding by known E,t. extimus has not been
<br />verified in those states. Statewide surveys in Arizona from 1993 to 1995 documented
<br />southwestern willow flycatchers at approximately 21 of over 400 sites surveyed (Muiznieks et
<br />ai. 1994, Sferra et ai. 1995, Spencer et ai. in prep.). Sferra et al. (1995) estimated a total of
<br />119 territorial males at the 21 extant locations.
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<br />Life History
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<br />The southwestern willow flycatcher is an insectivore, foraging within and above dense riparian
<br />vegetation, taking insects on the wing or gleaning them from foliage (Wheelock 1912. Bent
<br />1963).
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<br />The flycatcher begins arriving on breeding grounds in late April and May (Sogge and Tibbitts
<br />1992, Soggeetai. 1993, Sogge and Tibbitts 1994, Muiznieksetai. 1994, Maynard 1995, Sferra
<br />et al. 1995). Migration routes are not completely known. However, flycatchers, probably
<br />including sub-species E.t. brewsteri and E.t. adastus, have been documented migrating through
<br />drainages in Arizona that do not currently support breeding populations, including upper San
<br />Pedro River (Bureau of Land Management, unpublished data), Colorado River through Grand
<br />Canyon National Park (Sogge and Tibbitts 1992, Sogge et ai. 1993, Sogge and Tibbins 19~1.
<br />lower Colorado River (Muiznieks et ai. 1994, Spencer et al. in prep.), Verde River tributaries
<br />(Muiznieks et aI. 1994), and Cienega Creek (Bureau of Land Management, written
<br />communication).
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<br />Flycatchers of the genus Empidonax rarely sing during fall migration, so that a means "f
<br />distinguishing subspecies without a specimen is not feasible (Blake 1953, Peterson and Challf
<br />1973). However, willow flycatchers have been reported to sing and defend winter territories III
<br />Mexico and Central America (Gorski 1969, McCabe 1991). Willow flycatchers winter III
<br />Mexico, Central America, and perhaps northern South America (Phillips 1948, Stiles and SkUI~h
<br />1989, Peterson 1990, Ridgely and Tudor 1994, Howell and Webb 1995).
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<br />Biological and Conference Opinions Glen Canyon BeachiHabitat-Building Flows 2/16/96
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