A medium-sized (5-6 inches) wood warbler, the Yellow-rumped Warbler occurs in two geographically-linked color groups. Summer males from the eastern (Myrtle) group are streaked gray above and white below with a black face mask, black breast, white chin, and conspicuous yellow patches on the head, wings, and rump. Summer males from the western (Audubon’s) group have more extensive black on the breast and a yellow throat, but are otherwise similar to eastern males. Females of both groups are duller and browner than the males, and all birds become dull brown above and pale below (while retaining the conspicuous yellow patches) during the winter. This species may be distinguished from the similarly-patterned Magnolia Warbler (Setophaga magnolia) by that species’ heavily streaked breast and broader tail. The eastern form of the Yellow-rumped Warbler breeds across Alaska, Canada, and at higher elevations in the northeastern United States; wintering in the southeastern U.S., the Mid-Atlantic region, the Pacific coast from Washington to California, and the West Indies. The western form breeds in the Pacific Northwest, the mountains of northern California, and in the interior west; wintering in the southern California and the southwest. Both forms winter from the U.S.border south to Central America; the western form also breeds locally in the mountains of Mexico and Guatemala. Yellow-rumped Warblers primarily breed in northern and high-mountain evergreen forest habitats. In winter, this species may be found in open forest, thickets, and scrub as well as locally in urban and suburban areas. Yellow-rumped Warblers primarily eat small insects and spiders, but, more so than most other wood warblers, this species also eats fruits and berries during the winter. In appropriate habitat, Yellow-rumped Warblers may be observed foraging for invertebrates and berries in the tree canopy or in the undergrowth. Birdwatchers may also listen for this species’ song, a series of high-pitched warbling notes petering out at the end. Yellow-rumped Warblers are primarily active during the day, but, like many migratory songbirds, this species migrates at night.