Empidonax flycatchers are notoriously difficult to visually identify because of their similar appearances. On breeding grounds, when they are on territory and in full song, their generally unique vocalizations make identification easier, but outside of the breeding season, they are less vocal and more challenging to identify. There is also added confusion outside of the breeding season because multiple Empidonax species share the same migratory routes and wintering grounds. Thus, although the geographic distribution and timing of breeding Empidonax species is well understood, the exact timing and migratory paths of many Empidonax are much less understood.
Large-scale citizen science projects, such as eBird and iNaturalist, have revolutionized our ability to reconstruct migratory patterns of birds across the continent at an unprecedented level of accuracy because of the sheer number of observers. However, for difficult to identify species, such as flycatchers, there may be inaccuracies in migration patterns. For example, we examined photographic spring reports on eBird and iNaturalist of Yellow-bellied Flycatcher (Empidonax flaviventris) in the United States. We hope to publish the results in the near future. However, in the meantime, our preliminary results of examining only those records with photographic or audio documentation, it appears that nearly all birds reported as Yellow-bellied prior to May 5 have been misidentified, with most turning out to be Acadian Flycatcher and Eastern Wood-Pewee. Here, we discuss the main identification features of Yellow-bellied Flycatcher and how to separate it from the other similar eastern congeners such as Acadian Flycatcher, Least Flycatcher, Eastern Wood-Pewee and Western Flycatcher.
The following text and plate are extracts from our recently published Field Guide to North American Flycatchers; Empidonax and Pewees available at all major booksellers. In the text below, we will often refer to primary projection, tail width and contrasts in relative terms such as “medium”, “weak/short” and “strong/long”. The key in the front of the book will be helpful to quantify what these terms mean.
Click on the images on this page to see them full-sized and with notes.
Yellow-bellied Flycatcher is a small flycatcher with a distinctive yellow-green overall coloration. Focus on the medium to long primary projection, bold and strongly contrasting wingbars relative to black wing color and mantle, and strong wing panel contrast (due to lack of pale edges to primary feathers). Eye-ring is complete, bold, and crisp. It has a medium-length bill with a completely pale lower mandible. Its tail is relatively short and narrow. Chest and underparts are greenish-yellow with weak upper/underpart contrast. Crown is round and forehead angle is moderate. Often observed flicking its wings and tail. Yellow-bellied is a shy bird, preferring shaded understory or inner canopy rather than open or shrubby areas on both breeding and wintering grounds. Adult molt is completed on wintering grounds.
Call is a sharp “pip,” like Acadian, but higher pitch than Hammond’s. Commonly heard at dawn and dusk, its “che-bunk” song is very similar to the “che-bek” song of Least, but slightly longer and at a lower frequency. Yellow-bellied’s “che-bunk” is also preceded by a very short “pip” that can be difficult to discern in the field, but in spectrograms is unlike Least. Yellow-bellied gives a “pwee” song at dusk, akin to that of wood-pewees but shorter.
Yellow-bellied breeds in the boreal forests of the taiga from central Alaska east across Canada to Newfoundland. On breeding grounds it frequents spruce forests on the edges of bogs. It winters in Central America and migrates through eastern North America. Spring migrants primarily take a western circum-Gulf path through Texas, arriving in Texas no earlier than the first week of May. Northbound migrants then travel up the mid-continent, avoiding most of the southeastern United States (e.g., rare in Louisiana in spring). Arrives on breeding grounds in late May or even early June. Fall migration commences in the north in early Aug., but birds move quickly south, arriving on the Gulf coast and in Mexico by mid-Aug. Southbound migrants have a more easterly route, passing through Louisiana on their way down the Texas coast.
A small number of southbound migrants transit through Florida and Cuba and possibly across the Gulf from Louisiana. It departs from wintering grounds in Central America in late Apr. It is a rare vagrant to the Pacific coast in late fall, but virtually unrecorded anywhere in the United States during winter.
Least Flycatcher has a shorter primary projection than Yellow-bellied (note that the spacings between the outermost primary tips are wider than the inner primary tips, unlike the narrower, more even gaps in Least). Least’s white throat also gives it a stronger upper/underpart contrast than Yellow-bellied. Least’s eye-ring is messier or fuzzier.
Acadian Flycatcher has longer bill, stronger upper/underpart contrast, and wider tail than Yellow-bellied.
Eastern Wood-Pewee is larger, grayer and has very long primary projection. It often shows streaking on the undertail coverts.
Although ranges typically do not overlap, there is considerable confusion with a vagrant Western Flycatcher. Western has a tendency to occur as a late fall and winter vagrant along the gulf and east coast. Teardrop-shaped eye-ring and crest of Western are diagnostic when apparent. Western has weak wing panel contrast because of pale edges to primary feathers; Yellow-bellied generally lacks pale edges to primary feathers. Note also that the pale edges to secondaries on Western extend closer to the lower wingbar than in Yellow-bellied.
If you want to add anything to the discussion, please send me an email or leave a comment below. Thanks for looking!
Kaufman, K. (1990). A Field Guide to Advanced Birding: Birding Challenges and How to Approach Them. Houghton Mifflin Company, Boston, MA, USA.
Whitney, B. and K. Kaufman. 1986b. The Empidonax Challenge: looking at Empidonax. Part IV: Acadian, Yellow-bellied, and Western flycatchers. Birding 18: 315-327.
Heindel, M. and P. Pyle. (1999). Separating Western and Yellow-bellied Flycatchers in the field. Birder's Journal 8:78-87.
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