cowbird (redirected from Molothrus)

cowbird, New World bird of the blackbird and oriole (hangnest) family. The male eastern, or common, cowbird is glossy black, about 8 in. (20 cm) long, with a brown head and breast; the female is gray. Most cowbirds lay their eggs in the nests of smaller bird species, victimizing especially vireos, sparrows, and flycatchers. Sometimes the alien egg is ejected or buried under a new nest floor or the nest is abandoned, but usually the host bird incubates the egg and feeds the voracious intruder while its smaller offspring are starved or crowded out. Cowbirds eat seeds but feed chiefly on insects, following behind grazing cattle in order to capture the insects stirred up in this way—hence the name cowbird and the earlier name buffalo bird. Related birds are the bronzed, the California, the dwarf, the Nevada, and the red-eyed cowbirds. Cowbirds are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Passeriformes, family Icteridae.

---

cowbird

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.