Yellow Warblers are bright yellow birds. Their upperparts have a slight greenish tinge, and their tails are greenish yellow. Their heads and faces are plain, without lines or streaks. Males have reddish streaks down their breasts and bellies. Females are also yellow, but not as bright as males, and they lack red streaks. Females and immatures show a fine, yellowish eye-ring. First-year birds are drab yellow-gray, with yellow undertail coverts.