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The willow flycatcher (''Empidonax traillii'') is a small insect-eating,
neotropical The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In bioge ...
migrant
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
of the
tyrant flycatcher The tyrant flycatchers (Tyrannidae) are a family of passerine birds which occur throughout North and South America. They are considered the largest family of birds known to exist in the world, with more than 400 species. They are the most di ...
family. There are four subspecies of the willow flycatcher currently recognized, all of which breed in North America (including three subspecies that breed in California). ''Empidonax'' flycatchers are almost impossible to tell apart in the field so biologists use their songs to distinguish between them. The binomial commemorates the Scottish zoologist
Thomas Stewart Traill Thomas Stewart Traill (29 October 1781 – 30 July 1862) was a British physician, chemist, meteorologist, zoologist and scholar of medical jurisprudence. He was the grandfather of the physicist, meteorologist and geologist Robert Traill Om ...
.


Description and ecology

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. At one time, this bird and the alder flycatcher (''Empidonax alnorum'') were considered to be a single species, Traill's flycatcher. The willow and alder flycatchers were considered the same species until the 1970s. Their song is the only reliable method to tell them apart in the field . Their breeding habitat is
deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...
thickets, especially
willow Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist s ...
s and often near water, across the United States and southern
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world ...
. They make a
cup nest A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American robin or Eurasian bl ...
in a vertical fork in a shrub or tree. These neotropical birds migrate to
Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Gua ...
and
Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...
, and in small numbers as far south as
Ecuador Ecuador ( ; ; Quechuan languages, Quechua: ''Ikwayur''; Shuar language, Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechuan ...
in South America, often selecting winter habitat near water. Willow flycatchers travel approximately each way between wintering and breeding areas. They wait on a perch near the top of a shrub and fly out to catch insects in flight, also sometimes picking
insect Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, Thorax (ins ...
s from foliage while hovering. They may eat some
berries A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone or pit, although many pips or seeds may be present. Common examples are strawberries, raspb ...
. This bird's song is a sneezed ''fitz-bew''. The call is a dry ''whit''. This bird competes for habitat with the alder flycatcher where their ranges overlap.


Food resources

Willow flycatcher feed on insects, and common hoverflies '' Syritta pipiens'' have been found in their fecal samples.


Subspecies

The subspecies are best distinguished from each other by their songs. In addition, the four subspecies have significant genetic differences based on mitochondrial DNA analysis. Their winter ranges have been elucidated using mitochondrial DNA genetic studies of 172 birds sampled in winter combined with plumage coloration and morphological differences. The four subspecies of the willow flycatcher are:


''E. t. brewsteri'' – Little willow flycatcher

The little willow flycatcher (''E.t. brewsteri'') is the Pacific slope subspecies of the willow flycatcher. Described by Oberholser in 1918, it breeds in California from Tulare County north along the western side of the Sierra Nevada, and in Oregon and Washington west of the Cascade range.


''E.t. adastus''

The Great Basin/Northern Rockies subspecies of the willow flycatcher (''E. t. adastus'') breeds in California east of the Sierra/Cascade axis, from the Oregon border into Modoc County and possibly into northern Inyo County. Populations at high elevation just east of the Sierra Nevada crest but south of Modoc County are assumed to be ''E. t. brewsteri''. There has been very little study of ''E. t. adastus'' in California. It was described by Oberholser in 1932.


''E. t. extimus'' – Southwestern willow flycatcher

The southwestern willow flycatcher (''E. t. extimus'') is a federally
endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...
subspecies and it is known to be found in Arizona, California, Colorado, Nevada, New Mexico, Texas, and Utah. It was listed in 1995, at which time it was known to breed at only about 75 sites in riparian areas throughout the American southwest. The known breeding population was estimated at between 300 and 500 pairs. Breeding occurs from near sea level on the Santa Margarita River to at the
South Fork Kern River The South Fork Kern River is a tributary of the Kern River in the Sierra Nevada of the U.S. state of California. It is one of the southernmost rivers on the western slope of the mountains, and drains a high, relatively dry plateau country of a ...
and at upper San Luis Rey River in California and to over in Arizona, southwestern Colorado, and north-central New Mexico. The largest remaining population in California is on the South Fork Kern River, Kern County. In southern California, this subspecies breeds on the San Luis Rey River, at
Camp Pendleton Marine Corps Base Camp Pendleton is the major West Coast base of the United States Marine Corps and is one of the largest Marine Corps bases in the United States. It is on the Southern California coast in San Diego County and is bordered by ...
, the Santa Margarita River and Pilgrim, De Luz, French, and Las Flores creeks; as well as on the
Santa Ynez River The Santa Ynez River is one of the largest rivers on the Central Coast of California. It is long, ArcExplorer GIS data viewer. flowing from east to west through the Santa Ynez Valley, reaching the Pacific Ocean at Surf, near Vandenberg Space Fo ...
. In 1996, breeding was confirmed along the Arizona side of the lower
Colorado River The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid watershed that encompasses parts of seven U.S. sta ...
at Lake Mead Delta and at Topock Marsh. Examination of museum specimens of 578 migrating and wintering ''E. t. extimus'' indicating that
Guatemala Guatemala ( ; ), officially the Republic of Guatemala ( es, República de Guatemala, links=no), is a country in Central America. It is bordered to the north and west by Mexico; to the northeast by Belize and the Caribbean; to the east by H ...
to
Costa Rica Costa Rica (, ; ; literally "Rich Coast"), officially the Republic of Costa Rica ( es, República de Costa Rica), is a country in the Central American region of North America, bordered by Nicaragua to the north, the Caribbean Sea to the ...
constitutes the main winter range. This species is experiencing population declines throughout the Southwest due to habitat loss/alteration and invasive species. Saltcedar ('' Tamarix ramosissima)'' is an invasive species found throughout the Southwest and has replaced essential vegetation, by outcompeting native species, in riparian areas where the Southwest Willow flycatcher is found, which could be a contributing factor in this species decline. In two sites, one in Arizona and the other in New Mexico, native trees were able to replace patches of tamarix and populations of willow flycatchers increased. It was documented that 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, it's important to note that because willow flycatchers can and do breed, in some locations, within Saltcedar habitat it can serve as vital habitat in the recovery of this species. The San Pedro River Preserve was purchased by the
Nature Conservancy The Nature Conservancy (TNC) is a global environmental organization headquartered in Arlington, Virginia. it works via affiliates or branches in 79 countries and territories, as well as across every state in the US. Founded in 1951, The Nat ...
to preserve habitat for this subspecies.
North American beaver The North American beaver (''Castor canadensis'') is one of two extant beaver species, along with the Eurasian beaver (''Castor fiber''). It is native to North America and introduced in South America (Patagonia) and Europe (primarily Finland an ...
s (''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. This subspecies was described by A.R. Phillips in 1948.


''E. t. traillii''

The eastern
nominate Nomination is part of the process of selecting a candidate for either election to a public office, or the bestowing of an honor or award. A collection of nominees narrowed from the full list of candidates is a short list. Political office In the ...
subspecies of the willow flycatcher (''E. t. traillii'') was described by
Audubon The National Audubon Society (Audubon; ) is an American non-profit environmental organization dedicated to conservation of birds and their habitats. Located in the United States and incorporated in 1905, Audubon is one of the oldest of such organ ...
in 1828. It breeds from the eastern coast of the United States to the western
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
.


References


External links

* * * * * * * {{Taxonbar, from=Q903847 willow flycatcher Birds of North America Native birds of Western Canada Native birds of Eastern Canada Birds of the United States willow flycatcher Willow flycatcher