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Western flycatcher
Conservation status
Least Concern  (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Passeriformes
Family:	Tyrannidae
Genus:	Empidonax
Species:	E. difficilis
Binomial name
Empidonax difficilis Baird, 1858
Synonyms
Empidonax occidentalis Nelson, 1897

The western flycatcher (Empidonax difficilis) is a small insectivorous bird in the family Tyrannidae. It is native to western North America, where it breeds in the Rocky Mountains and Pacific Coast forests and mountain ranges from California to Alaska and south to central Mexico; northern populations migrate south to Mexico for the winter.

Taxonomy

The western flycatcher was recognized as a single species until 1989, when the American Ornithologists’ Union split it into two different species: the Pacific-slope flycatcher (E. difficilis) of coastal western North America and parts of the western Rocky Mountains, and the Cordilleran flycatcher (E. occidentalis) of the interior Rocky Mountains, with both species wintering in Mexico. Both species looked virtually identical to one another, with the split being based on differing breeding habitats and apparent differences in songs and calls. The split was recognized until 2023, when the American Ornithologists’ Union and International Ornithological Congress again lumped both species due to a lack of consistent vocal, genetic, morphological differences and extensive hybridization across much of their range.

Subspecies

There are five subspecies recognized:

• E. d. difficilis, from southeastern Alaska south to the Sierra San Pedro Mártir of Baja California, Mexico

• E. d. insulicola, the Channel Islands of southern California

• E. d. cineritius, mountains of southern Baja California Sur, Mexico

• E. d. hellmayri, Breeds in the interior Rockies from Canada south to northern Mexico, winters in central and southern Mexico

• E. d. occidentalis, the Sierra Madre del Sur of Guerrero and southern Oaxaca, Mexico

The latter two subspecies were previously thought to comprise the "Cordilleran flycatcher".

Description

Adults have olive-gray upperparts, darker on the wings and tail, with yellowish underparts; they have a conspicuous teardrop-shaped white eye ring, white wing bars, a small bill and a short tail. It differs only subtly from most Empidonax flycatchers in North America, but its breeding habitat and call are different. Many species of this genus look closely alike. The best ways to distinguish species are by voice, by breeding habitat, and by range.

DNA testing in 2014 confirmed a new field mark, involving the extent of buffy edging on the secondaries, to reliably distinguish this species from the yellow-bellied flycatchers.

The song includes notes represented as pseet, ptsick, seet usually sung rapidly together. In Pacific birds, the ptsick or ptik note has the first syllable higher-pitched than the second—this was previously seen as the only difference between their calls and those of the "Cordilleran" flycatcher (Sibley 2000). The male's typical position call is a loud and distinctive pit pete or tse-seet, but some give a "rising tsweep" or a "slurred tseeweep".

Distribution

These birds migrate to Mexico for the winter, where the Mexican central-southern birds are resident. The non-resident birds are on the western coast from Jalisco northwards, and then to inland regions, in a corridor strip on the western flank of the Sierra Madre Occidental.

Habitat

The western flycatcher inhabits either coniferous or deciduous forests. In its range it enters mixed woods, Douglas fir forests, redwood forests, pine-oak forests, and many other wooded environments including riparian woodlands. As of November 2019, there has been one case of these West Coast birds showing up on the East Coast, in Palmyra, New Jersey. The preferred breeding habitat is usually near running water. They make a cup nest on a fork in a tree, usually low in a horizontal branch. Females usually lay two to five eggs.

Diet

As a flycatcher it will wait on a perch and when it sees a flying insect it will fly out to catch it in flight (hawking), and will also pluck insects from foliage while hovering (gleaning). They also enter swarms of gnats or mosquitoes. They fulfill an important role in keeping insect populations in check, particularly mosquitoes, and they also eat caterpillars and spiders.

References

1. BirdLife International (2019). "Empidonax difficilis". IUCN Red List of Threatened Species. 2019: e.T22699871A137994099. doi:10.2305/IUCN.UK.2019-3.RLTS.T22699871A137994099.en. Retrieved 12 November 2021.
2. ^ "Tyrant flycatchers – IOC World Bird List". www.worldbirdnames.org. Retrieved 2023-07-29.
3. American Ornithology Society (6 July 2023). "Species lump for the Western Flycatcher; species status for the goshawk of North America; and species splits in several Caribbean birds among 2023 Check-list changes". American Ornithological Society. Retrieved 12 July 2023.
4. Association, American Birding (2022-12-06). "North American Birds: Vol. 73, No. 2". American Birding Association. Retrieved 2023-07-29.
5. Rush, Andrew C.; Cannings, Richard J.; Irwin, Darren E. (November 2009). "Analysis of multilocus DNA reveals hybridization in a contact zone between Empidonax flycatchers". Journal of Avian Biology. 40 (6): 614–624. CiteSeerX 10.1.1.474.2085. doi:10.1111/j.1600-048X.2009.04681.x.
6. Pieplow, Nathan (13 June 2011). "The "Western" Flycatcher Problem". Earbirding. Retrieved 2019-03-14.
7. Engel, Joshua (26 November 2014). "A first for Illinois, discovered in The Field Museum's collection". Field Museum of Natural History. Retrieved 19 February 2022.
8. Engel, Joshua (2 December 2014). "Follow up: A first for Illinois, discovered in the Field Museum's collection". Field Museum of Natural History. Retrieved 19 February 2022.
9. "Pacific-slope Flycatcher - eBird". ebird.org. Retrieved 2020-09-25.

• Sibley, David Allen (2000). The Sibley Guide to Birds. Alfred Knopf. p. 324. ISBN 0-679-45122-6.

External links

• Videos, photos, and sounds at the Internet Bird Collection
• Pacific-slope flycatcher at USGS
• Pacific-slope flycatcher photo gallery VIREO
• Article with photos at Bob Steele Phoptography

• Videos, photos and sounds - Internet Bird Collection
• Photos - VIREO Photo-High Res
• Photo; Article fwp.mt.gov (Montana Fish, Wildlife & Parks)

• IUCN Red List least concern species
• Empidonax
• Birds of Mexico
• Fauna of the California chaparral and woodlands
• Native birds of Alaska
• Native birds of the Northwestern United States
• Native birds of the West Coast of the United States
• Native birds of Western Canada
• Native birds of the Rocky Mountains
• Birds of the Great Basin
• Birds of the Rio Grande valleys
• Taxa named by Spencer Fullerton Baird
• Birds of the Sierra Madre Occidental
• Birds described in 1858