Tennessee Warbler Leiothlypis peregrina

Tiny, greenish warbler that breeds in boreal forest. Breeding males have lime-green back, pale blue-gray head, and dingy whitish underparts. Females and immatures generally show more yellow overall, but still dull. Note thin dark line through the eye, paler eyebrow, and whitish undertail coverts. Most similar to Orange-crowned Warbler. Look for cleaner, unstreaked breast and white (not yellow) undertail coverts. Loud song for such a small bird; usually three-parted series of accelerating chips. Often found around flowering trees during migration. Winters in Central and South America.