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. Larger and thicker-billed than warblers. Breeds in mature deciduous forest. Often sings nearly nonstop throughout the day; listen for repetitive musical phrases 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.