Subtly patterned brown-and-yellow warbler, known for constantly bobbing its tail. Often forages on the ground, unlike most other warblers. Breeding plumage shows a rufous cap. In fall and winter, look for pale eyebrow and dark line through the eye, diffuse streaks on underparts, and bright yellow undertail coverts. Two populations: “Western” is browner overall, brightest on the undertail coverts; “Yellow” is more suffused with yellow overall; they overlap extensively in range, especially during fall migration. Breeds in bogs and clearings in the boreal forest. In migration, found in a variety of open, shrubby habitats. One of the more common warblers wintering in the southern U.S.; also winters in the Caribbean and Yucatan Peninsula.