Adult male is bright yellow overall with rich chestnut streaks on the breast and flanks, plain yellow face with a large dark eye, greenish-yellow wings with paler yellow wingbars, relatively short tail, and black bill. Female lacks chestnut streaks and is not as bright yellow overall with plain face; may appear to have faint dusky streaking underneath. Immature can be very dull, often yellowish tan or even grayish; note long yellow undertail coverts, which make the tail look short, lack of contrasting marks on face, rather thick creamy white eye ring, and pale whitish edges to the folded tertials. In flight, all plumages show yellow tail spots.

Length: 13 (cm) Wingspan: 20 (cm)

Voice:

Song is highly variable combination of high-pitched notes and phrases, often described as "sweet, sweet, sweeter than sweet" with emphasis on the last note. Call is a rich syrupy chip note.

Habitat:

Willows, riparian areas, wet forest edges. During migration and winter, uses a variety of forest types.

Behavior:

Flits and forages at all levels of canopy. Nest is a very fine, soft cup on forked tree branch. During migration and winter, often joins flocks with other warblers.

Feeding:

Gleans foliage for a variety of caterpillars, moths, and other insects.