Appearance

A large warbler (12-13.5 cm). As is typical of Basileuterus, the plumage is dull, and the sexes are similar. The sides of the head are pale gray or grayish olive, with a dusky stripe through the eye, a darker streak along the sides of the crown, and a yellowish or golden streak down the center of the crown (giving rise to the English name Golden-crowned Warbler). The upperparts generally are dull olive or grayish. Throughout most of the range of the species, the underparts are dull yellow, but are white in one subspecies that occurs in south central Brazil and adjacent areas.

In Central America and in northern South America, Golden-crowned Warbler is sympatric with Rufous-capped Warbler (Basileuterus rufifrons), which differs by its cinnamon head and well-defined white supercilium. Golden-crowned Warbler is much more similar to Golden-bellied Warbler (Myiothlypis chrysogaster), with which Golden-crowned overlaps in locally northern South America. Golden-bellied Warbler is more olive above, lacks the dark line behind the eye of Golden-crowned Warbler, and has a yellowish supercilium. Two-banded Warbler (Myiothlypis bivitattus) may overlap locally with Golden-crowned Warbler, but differs by its more yellowish or olive supercilium.

The following description of nominate culicivorus is based on Ridgway (1902); see also Geographic Variation.

Adult: Sexes similar. Crown with two broad lateral black stripes. Stripe down center of crown pale yellowish olive; middle of this coronal stripe usually yellow (rarely orange-tawny or rufous, feathers with light yellowish olive tips). Rest of upperparts plain deep olive-gray; primaries edged with paler and clearer gray. Broad supercilium yellowish olive. Dusky spot on lores. Postocular stripe dusky. Auriculars grayish olive, the lower portion usually finely streaked with dull whitish or plae yellowish. Malars and underparts yellow, shading into light yellowish olive-green on sides and flanks.

Little information. The preformative molt probably is partial (Ryder and Wolfe 2009).

Iris: dark brown

Bill: dark brown

Tarsi and toes: brownish flesh

Bare part colors from Dickey and van Rossem (1938).

Total length: 12 cm (Stiles and Skutch 1989),  12-13.5 cm (Howell and Webb 1995), 13 cm (Hilty and Brown 1986).

Linear measurements (for nominate culicivorus; from Ridgway 1902):

male (n = 16), wing: mean 60 mm (range 58-64 mm)

                       tail: mean 51.8 mm (range 50-57 mm)

                       culmen (exposed): mean 9.2 mm (range 9-11 mm)

                       tarsus: mean 19.2 mm (range 18-20.5 mm)

female (n =12 ), wing: mean 57 mm (range 55-62.5 mm)

                        tail: mean 51.1. mm (range 48-54 mm)

                        culmen (exposed): mean 9.8 mm (range 9-10.5 mm)

                        tarsus: mean 19.1 mm (range 18.5-20 mm)

Mass: mean 10.5 g (range 9.5-12 g, n = 22, Trinidad; ffrench 1991)