Appearance

Vireos (Vireo) are small songbirds with dull, relatively unpatterned plumage, and a relatively stout, hooked bill. Brown-capped Vireo is a relatively small Vireo. In most subspecies of this widespread bird, the crown and nape are dark brown, contrasting with a white supercilium. The upperparts, including the wings and wing coverts, otherwise are olive brown. The throat and underparts are whitish, becoming yellower on the belly. The sexes of Brown-capped Vireo are similar; uveniles are duller, with pale cinnamon wingbars.

Warbling Vireo (Vireo gilvus) is a nonbreeding migrant that seasonally overlaps with Brown-capped Vireo, from Mexico south to Nicaragua. Warbling Vireo has a grayish (not brown) crown, and its upperparts are paler olive. Philadelphia Vireo (Vireo philadelphicus) is another nonbreeding migrant that overlaps seasonally with Brown-capped Vireo, from Mexico south to Colombia. Philadelphia Vireo has a grayish (not brown) crown, a yellow throat, and dark lores. Yet another migrant, Tennessee Warbler (Oreothlypis peregrina), overlaps with Brown-headed Vireo from Mexico south to northwestern South America; Tennessee Warbler has a slender, pointed bill, a short tail, a grayish or olive (not brown) crown, and its throat and breast often are washed with yellow. In South America, there are several species of greenlet (Hylophilus) with brown crowns, but all Hylophilus are smaller, with more pointed bills, and lack the white supercilium of Brown-capped Vireo; also, most species of greenlet occur in the lowlands, not in humid montane forest. Rufous-capped Greenlet (Hylophilus semibrunneus), which may be syntopic with Rufous-capped Greenlet, has a brighter, rufous brown crown.

The following description is based on Ridgway (1904) and on Wetmore et al. (1984); see also Geographic Variation.

Adult: Sexes similar. Crown olive brown. Upperparts otherwise grayish olive to brownish olive green. Supercilium white, bordered below by a dusky loral spot and postocular streak. Auriculars, throat, and upper breast grayish and white. Rest of underparts, as well as the edge of the wing and underwing coverts, pale yellow.

Iris: brown

Bill: maxilla dark brown, gray, or black; mandible horn or whitish with longitudinal blue gray streak

Tarsi and toes: blue gray, bluish gray

Bare parts color data from specimens in the Field Museum of Natural History and in the Louisiana State University Museum of Natural Science.

Total length: 11.5-12 cm (Howell and Webb 1995), 12 cm (Hilty and Brown 1986), 12.5 cm (Ridgely and Greenfield 2001b), 12.7 cm (Hilty 2003)

Linear measurements (from Wetmore et al. 1984; see also Ridgway 1904):

wing length, male: mean 64.0 mm (range 59.5-67.5 mm, n = 10)

                    female: mean 62.0 mm (range 59.0-66.0, n = 10)

tail length, male: mean 45.9 mm (range 43.3-49.6 mm, n = 10)

                    female: mean 45.0 mm (range 40.7-47.5, n = 10)

bill length (culmen from base), male: mean 11.6 mm (range 10.4-12.6 mm, n = 10)

                    female: mean 11.9 mm (range 10.9-12.5, n = 9)

tarsus length, male: mean 16.5 mm (range 15.3-17.3 mm, n = 10)

                    female: mean 17.0 mm (range 15.4-17.6, n = 10)

Mass: male, mean 12.5 g (range 12.0-13.0 g, n = 3; Colombia, Miller 1963); mean 13.1 g (range 12.8-13.4 g, n = 2; Mexico, Binford 1989)

        female, mean 12.3 g (range 11.8-13.1 g, n = 3; Colombia, Miller 1963)