Appearance

Black-cheeked Warbler is a small bird with a reddish brown crown, a white stripe above the eye, and a black cheek. Its back and tail are a dark olive gray and its belly, chest, and undertail coverts are pale tan or beige. As is typical of the genus Basileuterus, it is a relatively large parulid warbler, with a long, slightly rounded tail.

Although Black-cheeked Warbler is a distinctive species, it could be confused with Rufous-capped Warbler (Basileuterus rufifrons) in shade or bad light. Black-cheeked reliably can be distinguished from Rufous-capped Warbler by its darker cheek and white (not yellow) breast. Also, Black-cheeked often occurs at higher elevations than Rufous-capped.

Black-cheeked Warbler could also be confused with the similarly colored Sooty-capped Chlorospingus (Chlorospingus pileatus) if not seen well. These two species inhabit very similar habitat, and they often flock together. Black-cheeked Warbler can be distinguished from the chlorospingus by its smaller size, grayer back, more slender, bicolored bill, and rufous cap (Garrigues and Dean 2007).

The following description is based on Ridgway (1902) and Wetmore et al. (1984):

Adult: Sexes similar. Crown chestnut, with a lateral margin of black, with black lines converging on the center of the forecrown, sometimes forming a black spot. White or pale yellowish supercilium, extendint to nape. The sides of the nape are sooty blackish, and the mid portion of these parts, including the hindneck and the sides of the neck, are plain dark brownish gray or olive. The rump and uppertail coverts are olive, while the wings and tail are a dusky brownish gray. Throat whitish. Broad grayish breast band; flanks olive, center of belly and undertail coverts buffy white.

Immature: Crown and sides of head sooty brown. Supercilium dull, tinged with olive. Upperparts browner; wings with two narrow buffy wingbars. Underparts dull yellowish, washed with brownish on breast, sides, and flanks (Stiles and Skutch 1989).

Hatchling: skin pink, with sparse gray down (Curson et al. 1994).

There is little information on molts of Black-cheeked Warbler. The "post-juvenile" (= preformative) molt of this bird may be partial, but more study is required to prove this. First-years/adults have a complete postbreeding (prebasic) molt (Curson et al. 1994).

The bill is bicolored, with a pink mandible and dusky black maxilla. The tarsi and toes are pale brownish white, and the iris is dark brown iris (Wetmore et al. 1984). The inside of the mouth of nestlings is yellow (Ficken 1965).

Total length: 13.5 cm (Stiles and Skutch 1989)

Linear measurements (from Wetmore et al. 1984, nominate melanogenys):

male (n = 10)

wing length: mean 61.1 mm (range 56.5-66.5 mm)

tail length: mean 60.4 mm (range 58.1-62.3 mm)

bill length (culmen from base): mean 11.7 mm (range 10.3-12.7 mm)

tarsus length: mean 21.7 mm (range 20.0-23.0 mm)

female (n = 10)

wing length: mean 60.3 mm (range 58.8-62.1 mm)

tail length: mean 58.6 mm (range 54.7-61.0 mm)

bill length (culmen from base): mean 11.9 mm (range 11.3-12.7 mm)

tarsus length: mean 21.9 mm (range 20.7-23.5 mm)

Mass: mean 11.8 g (n = 9, sexes combined; Hartman 1961)