An unmarked vireo, the warbling is most often located by its song, which it delivers for hours. The birds tend to work mid and top parts of broad, leafy trees. Polytypic. Length 5.5".

Among the dullest of vireos, lacking wing bars and spectacles; gray with brownish or greenish tones to the upper parts. The face pattern is ill-defined, with a dusky postocular stripe and pale lores; white eyebrow lacks a dark upper border. The underparts are typically whitish. Fall: in fresh plumage, greener above with yellow wash on flanks and undertail coverts.

Two western subspecies, especially swainsoni, are smaller than the nominate eastern sub-species, have a slighter bill, and tend to be more olive above with a grayer crown. Eastern and western