The yellow warbler is 4 1/2 – 5 inches in length, with a sharp, fine bill. Its body is all yellow, with yellow-green wings, yellow wing bars, and yellow tail patches. The male has bright chestnut-red streaks on its breast. Its black eye is outlined by a thin yellow eye ring. Plumage varies somewhat by region, with Alaskan birds being grayer, and the Sonoran subspecies paler, than the eastern standard