Size and structure—large, full-bodied, long-billed—make the Prothonotary Warbler an unlikely candidate for confusion with other warbler species. It is also distinctive in plumage, with bright-yellow head and breast, greenish-yellow back, and bluish wings. When spread, the bluish upperside of the tail shows large white spots. The underside of the tail is mostly white, extending onto the undertail coverts. The Blue-winged Warbler is somewhat similar in coloration but has a dark line through the eye and prominent white wingbars, in addition to being considerably smaller and more slender.