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Status: Population size: 3.3 million Photo by Ohio Department of Natural Resources.

Willow Flycatcher
(Empidonax traillii)

This is a migratory species that breeds from Maine to British Columbia. Its breeding range extends as far south as southern parts of California and Arizona. Because it is restricted to river corridors in the more arid parts of the country it is especially vulnerable to human activity that degrades the habitat.

Identification
In addition to wingbars the Willow Flycatcher has a relatively flat forehead and a distinct peak on the rear crown. It also has a broad, straight-sided tail. It has a less obvious eye-ring than the Alder Flycatcher which it very closely resembles and can best be distinguished from it by voice. It can also be distinguished in part by breeding range since the Willow Flycatcher's breeding range extends further south.

Distribution and Population Trends
While its breeding range extends from Maine to British Columbia and south to southern California and Arizona, s. Missouri, s. Tennessee, n. Georgia and mountains of w. North Carolina, it generally does not breed in the higher elevations of the continental divide and in the drier states to the east.

The Breeding Bird Surveys data (1966-1996) showed a 1.3% annual population decrease for the U.S. and a 1.2% annual decrease for the continent. Six states (ME, MD, NJ, NY, ND, PA) showed significant population increases while MI, OR, and WA showed significant population decreases. One subspecies, Empidonax traillii extimus, of the southwestern U.S. is listed as endangered and is now extirpated from much of its originally described range. There is no evidence of further declines since its listing as an endangered species in 1995.

Ecology
This is a long distance migrant and all are migratory. Birds migrate over much of the southern U. S. to wintering sites in s. Mexico, Central America and n. South America. Based on tower kill data migration is most likely nocturnal. This is a late spring migrant and fall migration occurs in late summer to early fall.

The species generally nests in riparian sites that are moist, shrubby areas often with standing or running water. In Washington State it also nests in xeric uplands and in the central and eastern U.S. it uses both wet and dry upland sites. Nests are generally close to the ground in the crotches of shrubs or small trees near water. Usually 3-4 eggs are laid and incubation is about 14 days. Generally the female incubates the eggs. Both adults feed the young and food is primarily insects. Foraging occurs in the air and among various kinds of vegetation.

Brood parasitism by the Brown-headed Cowbird negatively affects nesting success. This varies both in time and location with some areas being more affected than others.

Threats
Habitat destruction and degradation plus overgrazing by livestock are the major causes of population decline. Large flood control dams which alter flooding cycles may affect nesting success since it is known that Willow Flycatchers will not attempt nesting in the absence of flowing water.

Conservation
Critical habitat for the subspecies listed as Endangered (Empidonax traillii extimus) was designated in 1997 in the three states (NM, AZ, and CA) where the largest populations are know to occur by the USFWS. Ultimately, survival of this subspecies will depend upon maintenance and restoration of riparian habitats.

What Can You Do?
Audubon's Important Bird Area program is a vital tool for the conservation of the Willow Flycatcher as well as other species. To learn more about the Important Bird Areas program and how you can help, visit: http://www.audubon.org/bird/iba/.

Information on where the Willow Flycatcher occurs and in what numbers is vital to conserving the species. Help in monitoring this and other species by reporting your sightings to eBird. A project of Audubon and the Cornell Lab of Ornithology, eBird is the world's first comprehensive on-line bird monitoring program: http://www.audubon.org/bird/ebird/index.html

If you own land that supports or has the potential for supporting the Willow Flycatcher, consider managing it in ways that would increase the numbers of the species. Rotating livestock on its grazing lands could also help reduce cowbird parasitism. Contact your state wildlife agency or your state Audubon office for more details.

References
Kaufman, Kenn. 2000. Birds of North America. Kaufman Focus Guides. Hillstar Editions L. C., Houghton Mifflin Company, New York, New York.

Sedgwick, James A. 2000. Willow Flycatcher (Empidonax traillii). In The Birds of North America, No. 533 (A. Poole and F. Gill, eds.). Ithaca: Cornell Laboratory of Ornithology; Philadelphia: The Academy of Natural Sciences; Washington, DC: The American Ornithologists' Union.

Sibley, D. A. 2000. The Sibley Guide to Birds. National Audubon Society. New York: Chanticleer Press, Inc.