The common brown-headed cowbird is the most widespread brood parasite in North America. Poly­typic. Length 7.5".

A smallish, compact and stocky blackbird with a short and thick-based bill, almost finchlike. Foraging birds are commonly seen on the ground with the tail cocked. Adult male: the glossy black body, with a greenish iridescence, contrasts with a brown head. The eyes are dark; the bill and legs are black. Adult female: dull brownish throughout, with darker wings and tail. The secondaries show crisp pale fringes. The face has a beady-eyed look due to dark eyes; the lores are pale, as is the area below the eyes. The whitish throat contrasts with the darker face; the underparts are obscurely streaked. The bill is dark,