The Flame-throated Warbler is characterized by, and named for, its bright and strikingly orange throat patch. Otherwise the upperparts are slate gray, with black in the center of the back, and the belly is white. Plumage varies slightly between males and females, and more significantly between juveniles and adults.
The Flame-throated Warbler is a distinctive species, and is not easily confused with other species within its small geographic distribution. The Tropical Parula (Parula pitiayumi) is superficially similar, but has a yellower (less orange) throat, has at least one white wing bar, and the center of the back is greenish (not black).
The following description is based on Wetmore et al. (1984) and Ridgway (1902):
Adult: Sexes very similar. Upperparts slate gray, with a triangular black patch on the upper back. Lores blackish, this color extending onto the auriculars in males but black less extensive on females (Stiles and Skutch 1989, Curson et al. 1994). Primaries blackish, with outer web narrowly edged with slate gray; secondaries blackish on inner web, slate gray on outer web. Rectrices blackish with outer webs edged slate gray. Throat and breast rich orange (sometimes almost flame scarlet). Flanks light gray. Belly and undertail coverts white.
Juvenile: Upperparts olive-gray, with a triangular black patch on the upper back. Lores and auriculars dusky; narrow buff postocular stripe. Wings and tail dusky; upper wing coverts narrowly tipped buff. Chin and throat orange-yellow, fading to buff on the belly.
Little information. There is a preformative molt that is partial; juvenile (first basic) wing coverts are retained. Basic molt is complete (Curson et al. 1994).
Iris: dark brown
Bill: mostly black; base of gonys and lower margin of mandibular rami dull orange-yellow
Tarsi and toes: dull mouse brown
Data from Wetmore et al. (1984).
Total length: 10.6-11.6 cm (Wetmore et al. 1984), 12 cm (Stiles and Skutch 1989)
Linear measurements (mm) of Flame-throated Warbler (Wetmore et al. 1984)
| || || wing|| tail|| culmen (from base)|| tarsus|
| male|| mean|| 63.2|| 47.6|| 13.0|| 17.3|
| n=10|| range|| 61.4-65.1|| 43.6-52.0|| 12.3-13.8|| 16.2-18.1|
| female|| mean|| 60.4|| 46.2|| 12.4|| 16.8|
| n=10|| range|| 57.0-65.0|| 42.8-50.7|| 10.6-13.1|| 16.0-17.6|
Mass: mean 9.5 g (n=7; Curson et al. 1994); mean 11 g (n=10; Sillett 1994)