any of a number of small American blackbirds (esp. Molothrus ater) often seen near cattle: cowbirds lay eggs in other birds' nests
See cowbird in American Heritage Dictionary 4
(kouˈbûrdˌ)
noun
Any of various blackbirds of the genus Molothrus, especially the common North American species M. ater, that lay their eggs in the nests of other birds and are often seen accompanying herds of grazing cattle.