Male: head, chest, and belly golden yellow; back olive; wings blue-gray; tail blue-gray with large white patches on the outer feathers; white undertail coverts. Female: upper parts olive; underparts golden yellow; belly pale yellow to white; wings blue-gray; tail blue-gray with large white patches on the outer feathers; white undertail coverts. 14 cm (5.5 in) in length. The Prothonotary Warbler has a long sharp bill and large black eyes. The song is a loud series of notes, sounding like sweet sweet sweet sweet sweet.
The breeding season begins in mid-April, peaks in May, and extends into July. Breeding habitat is closely associated with wet forest, including swamps, sloughs, and flooded bottomland hardwood forest. This species is a secondary cavity nester, using natural cavities, crevices, cavities created by another species, or nest boxes. The male stuffs cavities within his territory with moss. After the female chooses a nest site, she will add more moss or begin the nest building within the moss already placed by the male. The female lays 3-8 (usually 4-6) eggs that she incubates for 12-14 days. The young are altricial and fledge 11 days after hatching. The young usually remain in the nest area, being cared for by the adults for about a week after fledging.
Throughout the year this species is closely tied to water. The diet consists of insects and some crustaceans and snails. The Prothonotary Warbler moves among the lower branches of trees and shrubs searching for prey among the leaves and in rotten wood. During the winter, its diet expands to include some fruit and nectar. This species is a long-distance migrant.
The Prothonotary Warbler is a eastern species. During the breeding season, it occurs in appropriate habitat throughout the eastern states, and especially in the south. During the winter, this species is found from Mexico south to northern South America. During the breeding season, the Prothonotary Warbler occurs in appropriate habitat through most of Georgia, except in the mountainous regions.
Prothonotary Warbler populations have declined in some areas because of the drainage of bottomland hardwood forests and elimination of floodplain forests. This species is sometimes parasitzed by the Brown-headed Cowbird, but parasitism is lower than in many other species because it is a cavity nester. Brown-headed Cowbird females have difficulty entering the small cavities this species uses. When parasitized, the warbler will raise the cowbird young instead of or in addition to its own young.
The Prothonotary Warbler cannot be mistaken for very many other swampy bottomland forest species. The warbler that resembles most closely it is the Blue-winged Warbler. However, the Blue-winged Warbler has a black eye line and white wing bars, two features that the Prothonotary Warbler lacks.