Yellowthroats (Geothlypis) are medium sized warblers that are associated with aquatic habitats. The plumage of yellowthroats generally is olive brown above and yellow below, at least on the throat and breast; additionally, male yellowthroats have a broad black "mask" across the face, and in many species this mask is bordered above by yellow or white. Black-polled Yellowthroat is a relatively large yellowthroat. The male has a broad black mask on the face, and a black forecrown, but the mask does not have a pale upper border. The female is similar to females of several other species of yellowthroats: olive brown above and yellow below, with dusky olive flanks.
Common Yellowthroat (Geothlypis trichas) is smaller with pale (flesh colored) tarsi and a whitish to pale yellow belly Also, the male Common Yellowthroat has a whitish to grayish white border above black mask. These two species also differ in by voice. Gray-crowned Yellowthroat (Geothlypis poliocephala) is larger with a heavier bill and pale tarsi. Male Gray-crowned Yellowthroat has only a limited black face mask, and the female Gray-crowned has more prominent white crescents above and below the eye. Black-polled Yellowthroat is allopatric or parapatric to other species of yellowthroats. Male Black-polled is distinguished from most other species by the lack of a noticeable white, yellow or gray border above the black mask. In this respect, it is most similar to males of the allopatric Olive-crowned Yellowthroat (Geothlypis semiflava), but Olive-crowned has greener upperparts and lacks the cinnamon or ochraceous wash on the flanks of male Black-polled. Female Black-polled is less distinctive, and is similar to females of some other species, perhaps especially to female Hooded Yellowthroat (Geothlypis nelsoni).
The following description is based on Curson et al. (1994) and Dickerman (1970; juvenile); see also Ridgway (1902) and Geographic Variation.
Black-polled Yellowthroat is the darkest of the yellowthroats.
Adult male: Upperparts warm brownish olive with a dusky blackish crown. Underparts a rich, almost golden yellow, with a brownish cinnamon or ochre wash to the breast and flanks. Male has no distinct pale forecrown band; instead the black mask and forehead merge into a dusky blackish crown and then into the brownish olive of the nape and upperparts.
Adult female: Head dark olive gray with a pale supraloral and supercilium. Upperparts have a distinct dark grayish wash and underparts are a rich, dull yellow with the breast, flanks, and belly heavily washed with olive brown. In fresh basic plumages, has rich buffy-ochraceous edgings to the feathers of the underparts, somewhat obscuring the yellow (Dickerman 1970).
First-year male: Resembles adult male, but the black mask is incomplete, generally restricted to the lores and lower auriculars, and the crown is more olive brown than sooty-brown.
Juvenile: Similar to adult female, but slightly darker and browner above. Underparts duller than female, especially on the throat and upper breast.
Little information. One Black-polled Yellowthroat taken 7 September shows extensive prebasic molt (Dickerman 1970).
Bill: blackish, and noticeably longer and more slender than the bill of Common Yellowthroat (Geothlypis trichas).
Tarsi and toes: dark brownish.
Total length: 12.5-13 cm (Howell and Webb 1995), 13 cm (Curson et al. 1994)
wing length (chord): mean 58.1 mm (range 55-61 mm; n = 27; Dickerman 1970)
tail length: mean 58.0 mm (range 51-61 mm; n = 24; Dickerman 1970)
bill length (exposed culmen): 12.7 mm (n = 1; Ridgway 1902)
tarsus length: 21.6 mm (n = 1; Ridgway 1902)
wing length (chord): mean 54.8 mm (range 53-57 mm; n = 13; Dickerman 1970)
tail length: mean 53.5 mm (range 49-56 mm; n = 11; Dickerman 1970)
bill length (exposed culmen): 14 mm (n = 1; Ridgway 1902)
tarsus length: 20.3 mm (n = 1; Ridgway 1902)
male: mean 10.7 g (range 9.5-12.0 g, n = 8; Dickerman 1970)
female: range 9.5-9.7 g (n = 4; Dickerman 1970)