BLUE-WINGED WARBLER pl. 2 Vermivora pinus
4.75 in. (12 cm). This inhabitant of successional habitats in eastern North America has dramatically expanded its range to the north and northeast in the 1900s. Although the Blue-winged is very different in plumage pattern from the more northerly-breeding Golden-winged Warbler, these two species are closely related and frequently hybridize in the shifting zone where their ranges come into contact. Hybrids are discussed under Golden-winged Warbler (p. 133). The Blue- winged Warbler has a long, sharp bill and a bold, dark line through the eye in all plumages, along with white undertail coverts that contrast with the yellow underparts. The blue-gray wings with whitish wing bars and mostly extensive white in the outer three pairs of tail feathers are distinctive among warblers with plain olive upperparts and unmarked yellow underparts.
Description Generally green above and yellow on the crown and underparts, becoming white on the undertail coverts; all plumages show a dark line through the eye and pale (usually whitish) wing bars. Age and sex differences are slight; there is little seasonal change in plumage.
The Blue-winged is a medium-sized warbler with a moderately long tail and a rather long and sharply pointed bill; there is a strong seasonal change in bill color.