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Any of six passerine species related to New World blackbirds (family Icteridae) that exhibit brood parasitism. Cowbirds lay their eggs in the nests of other birds, usually one to each host nest. Young cowbirds, which displace nestlings or outcompete them for food, may grow larger than the foster parents. In parts of North America, the brown-headed cowbird (Molothrus ater) parasitizes the nests of more than 200 other bird species; others use the nests of only one or two kinds of oriole. Cowbirds forage on the ground, often associating with cattle in order to catch insects stirred up by the cows' hooves. The male of most species is a uniform glossy black, the female grayish brown.
This entry comes from Encyclopædia Britannica Concise. For the full entry on cowbird, visit Britannica.com.