The male Black-throated Green Warbler is distinctive with its black throat, yellow face, and olive crown. Within most of its eastern United States range, it is unlikely to be confused with any other species. Males of other western species are somewhat similar: Hermit Warbler has a yellow crown, Golden-cheeked Warbler has a black crown and eyeline, Townsend's Warbler has black cheeks. In fall, the yellow face of the Black-throated Green barely contrasts with the greener crown and cheeks. Blackburnian Warbler has a darker crown and cheeks and white streaks on the back. Townsend's Warbler also has darker cheeks. Hermit Warbler has a more uniformly yellow head and less streaking on the sides.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.