The edges of the wings are bluish gray, but the scapulars are olive green. The eyes of this species are large, dark and prominent against the bright yellow head. Compared to the bills of other warblers, the Prothonotary's black bill is relatively long and pointed. As in many passerine birds, the plumage of the female Prothonotary Warbler is similar to the male's, albeit less bright and less orange. Her head is tinted with olive, and there is little white in her tail.
Juveniles are primarily a dull brownish olive on the crown, nape, and upper parts.
The sides of the head, the throat, and the upper breast are washed-out yellow. The belly is yellowish white and the flanks are grayish olive. The Prothonotary Warbler breeds throughout the eastern United States and also in southern Canada. They prefer areas with stagnant water, such as swamps, ponds, wet bottomlands, and lowland forests subject to flooding. This species is primarily insectivorous, eating ants, mayflies, beetles, and the larvae of aquatic insects.