Small plain vireo of tropical forest and woodland in lowlands. Usually stays fairly high in trees and likely to be overlooked unless its rather tuneless, monotonously repeated song is learned. Identified by a combination its gray head (in Mexico and Central America) with a diffuse whitish eyering; whitish underparts with a yellowish wash on the sides; and plain olive upperparts. Head of birds from eastern Panama to South America is olive, with a whitish eyering.