The identification of the various Empidonax species in British Columbia ranges from difficult to extremely complex, and the Yellow-bellied Flycatcher is no exception to this. Correct identification will always be dependent on the assessment of multiple field marks rather than just a single feature. Although it is relatively distinct due to its (usually) extensive yellowish underparts, it does overlap in plumage characteristics with several other members of the genus and its identification, especially outside of the breeding season, is always going to be challenging. It is most similar in plumage to the much more common and widespread Pacific-slope Flycatcher, and fall vagrants anywhere in southern or central B.C. would most likely be confused with this species. Pacific-slope Flycatcher also has extensively yellowish underparts, but is a distinctly browner species (vs. greenish-olive in Yellow-bellied Flycatcher) and often shows a more prominent peak on the hindcrown (the head of Yellow-bellied is generally much more evenly rounded). The tertials and secondaries of Pacific-slope Flycatcher have less well-defined whitish to buffy feather edges, although Yellow-bellied Flycatchers in worn plumage can approach this characteristic. The wings also average overall browner and contrast less with the colour of the upperparts, but, again, Yellow-bellied Flycatchers in worn plumage can appear similar. During the breeding season, the distinctive song and call of Pacific-slope Flycatcher should serve to distinguish the species if it is heard, but this would not be possible with silent fall vagrants.
Immature and dull adult Yellow-bellied Flycatchers can show reduced or paler yellow on the underparts, with almost no yellow present in extreme cases, and can easily be confused with Least Flycatcher, which often occurs in the same areas as Yellow-bellied. These individuals are best identified by a combination of the overall more greenish-olive plumage (plumage more greyish-olive in Least), the less obvious contrast between the greenish-olive head and pale throat (contrast is better defined in Least), more almond-shaped eye-ring that forms a short point behind the eye (eye-ring usually rounded in Least, although some Yellow-bellied can show a similar eye-ring), entirely pinkish or orange lower mandible (lower mandible usually with a dusky tip in Least), and slightly longer primary projection. Some adult Least Flycatchers molt into fresh plumage on the breeding grounds, and thus can be washed with yellow on the underparts and may appear similar to Yellow-bellied Flycatcher, but these individuals can still be identified based on the above field marks.
The only other Empidonax species in B.C. that molts into fresh plumage prior to fall migration is Hammond’s Flycatcher, but this species should still be easily separated from Yellow-bellied Flycatcher despite the yellowish wash on the underparts at this time of year. Hammond’s Flycatcher is much greyer on the head and upperparts, although juveniles can be washed with olive on the back. It also has a distinctly large head, short bill, and long primary projection, giving it a distinctive structure. The lower mandible is primarily dark in Hammond’s Flycatcher, with some orange or pink at the base, and this feature alone should be sufficient to separate this species from Yellow-bellied Flycatcher with its entirely orange or pink lower mandible.
Source: Sibley (2000)
| The male’s song is a low, hoarse, abrupt chebunk or killink, sometimes reduced to a single syllable psek or kik, and is repeated every 6-10 seconds for prolonged periods. The typical two-syllable song is very reminiscent of the song of the Least Flycatcher, but is lower-pitched, softer, and buzzier without the strong emphasis; the single-syllable song can also be confused with the pik call of the Downy Woodpecker. The commonly-heard call note is a short, clear, rising, whistled tuwee or chee-weep. During aggressive encounters, often gives a abrupt, buzzy brrrrt from flight. Other calls include a short, whistled pwee, a sharp, descending pyew (given by migrants), a long, plaintive peehk, and a sharp wsee. Source: Sibley (2000); Gross and Lowther (2001) |
Courtship
Pair formation occurs immediately after arrival on the breeding grounds. The typical song, which functions both for territory establishment and mate attraction, is given from high, exposed perches within the territory (often from the tops of coniferous trees). The male’s ‘song flight’ is generally considered to be related to pair formation. During this flight display, which usually occurs in the predawn hours or at dusk, the male gives alternating chebenk and tu-wee calls. To initiate copulation, the female crouches on a branch and flutters her wings.
Nest
Nest construction begins immediately after arrival on the breeding grounds, usually in late May or early June; the nest is built solely by the female. The nest is a cup of rootlets, plant stems, moss, and grasses that is usually situated on the ground (rarely as high as 2 m from the ground) within a depression in moss, soft wood, roots (including upturned tree roots), or mud; it is lined with dead grasses, rootlets, conifer needles, and moss rhizoids. The dimensions of the nest are ~8 cm wide and 9-10 cm deep, with an internal cup 2.5-5 cm deep. The nest is very well hidden and is generally completely concealed from above by overhanging roots or vegetation.
Eggs
A single clutch of 3-4 (5) eggs is laid between mid-June and early July and is incubated by the female for 12-15 days before hatching. The smooth, slightly glossy eggs are whitish, often with fine brown or reddish-brown to pinkish or buffy speckling and spotting. Eggs are present in B.C. between mid-June and mid-July. This species is rarely a victim of Brown-headed Cowbird nest parasitism.
Young
The young are fully altricial at hatching, with a sparse covering of brownish-olive down. The young are tended by both parents for 13 days before fledging, after which time they remain with the parents for up to 9 days before dispersing and becoming independent. Nestlings and dependent fledglings are found in B.C. between early July and late July.
Source: Baicich and Harrison (1997); Campbell et al. (1997); Gross and Lowther (2001)
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This species primarily consumes flying insects throughout the year, with most prey captured in the air during short flights, or ‘sallies’ (behaviour known as ‘flycatching’ or ‘hawking’). Some prey is acquired through ‘sally-gleaning’ in which a flying bird picks the prey off of twigs or leaves; this foraging style is usually employed by birds that are foraging within a canopy of vegetation. This species also occasionally lands briefly on the ground to grab a prey insect, quickly returning to an elevated perch. Most foraging birds do not return to the same perch after sallies, except those that are returning from foraging on the ground. There are occasional reports of this species consuming berries on the breeding grounds (specifically, Poison-ivy berries in eastern North America), even when flying insects are present, but this appears to be infrequent.
Source: Gross and Lowther (2001)
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