thumb |right|Summer breeding and winter ranges of willow flycatcher subspecies from [[United States Geological Survey|USGS southwestern willow flycatcher survey protocol]]
The willow flycatcher (Empidonax traillii) is a small insect-eating, migrant bird of the tyrant flycatcher family native to North America.
Taxonomy
The willow flycatcher was included by the Franco-American ornithologist John James Audubon in his book The Birds of America based on a specimen collected in the "woods along the prairie banks of the Arkansas River". The section of the book containing the willow flycatcher was published in 1828. There are two variants of the plate illustrating the flycatcher. On one the binomial name is given as Muscicapa trailli and on the other as Muscicapa traillii. The latter spelling was used in 1831 by Audubon when describing the species in his Ornithological Biography that was published to accompany the plates and is now the accepted spelling. The specific epithet was chosen by Audubon to honour his friend the Scottish physician and zoologist Thomas Stewart Traill. The willow flycatcher is now one of 14 species placed in the genus Empidonax that was introduced in 1855 by the German ornithologist Jean Cabanis. In two sites, one in Arizona and the other in New Mexico, native trees were able to replace patches of saltcedar and populations of willow flycatchers increased. In these sites 90% of the willow flycatcher's nests were found in native vegetation, only 10% were in mixed vegetation (native species and saltcedar) and few were in areas dominated by saltcedar. However, because willow flycatchers can and do breed in some locations within saltcedar habitat, it occasionally serves as vital habitat in the recovery of this species.
The San Pedro River Preserve was purchased by the Nature Conservancy to preserve habitat for this subspecies. NatureServe considers the subspecies Imperiled. North American beavers (Castor canadensis) are thought to play a critical role in widening riparian width, openings in dense vegetation, and retention of surface water through the willow flycatcher breeding season.
E. t. traillii (Audubon, 1828)
The eastern nominate subspecies of the willow flycatcher (E. t. traillii) was described by Audubon in 1828. It breeds from the eastern coast of the United States to the western Rocky Mountains.
Description
Adults have brown-olive upperparts, darker on the wings and tail, with whitish underparts; they have an indistinct white eye ring, white wing bars and a small bill. The breast is washed with olive-gray. The upper part of the bill is gray; the lower part is orangish.
{| class="wikitable" style="font-size: 87%;"
|-
! colspan="2" | Standard Measurements For example, flies of the order Diptera made up the majority of adult willow flycatcher diets in Ontario, Canada, but only composed 10.6% of the diet of California flycatchers, who instead favor Lepidopterans, mayflies, and snakeflies. They are "sit-and-wait" predators, remaining on a perch near the top of a shrub and flying out to catch insects on the wing, but are also reported to glean insects off of leaves and stems.
References
<!-- CaribbJSci43:87. Condor107:765. WilsonBull18:47 (compare to current Ohio checklist http://www.ohiobirds.org/publications/OBRClist.pdf). -->