Bell’s vireo adult upperparts are grayish; the eye ring and lore (the region just in front of the eye) are indistinctly whitish, looking faintly like eyeglasses. The wing bars are whitish; the upper wing bar often is short, or indistinct, or absent. Underparts are whitish with some yellowish tones. The tail appears long because the wings are short. The song is a two-part series of jumbled, harsh notes. The first part “asks a question” and the second part “answers it,” because the first phrase ends in a rising tone and the second descends.
Similar species: The white-eyed vireo is similar in habits and song, but it is more assertively olive and yellow, has unmistakable white wing bars, and has yellow “spectacles.” Also, the eyes of adults have white irises, if you can get close enough to see them. Also, it is easy to confuse warblers with vireos. Be sure to check the bill on any slowly foraging, pale or drab-colored warblerlike bird, for it may be a vireo. The bill of the vireo is relatively thick, until the tip, and it has a small hook that can be seen from below. Warblers’ bills are narrow and taper to a sharp point. Flycatchers, too, can also be confused with vireos. Flycatchers have a chunkier body and somewhat crested or angled head shape, and typically flutter out from a perch to snatch flying insects, then return to the same perch.