Plain olive-green above and whitish below with no wingbars. Red eye of adults is not always easy to see; immatures have brown eyes. Dark stripe through and above eye. Thicker bill than warblers, body about the same size. Found in forested areas with deciduous trees. Tends to sing later in the day than other songbirds. Listen for their monotonous song coming from the treetops. Often with flocks of chickadees and warblers during migration. Winters in South America, where it could be confused with the very similar Chivi Vireo. Best distinguished by voice.