Brown-headed Cowbird

The Brown-headed Cowbird, Molothrus ater, is a small icterid.

Adults have a short finch-like bill and dark eyes. The adult male is mainly irridescent black with a brown head. The adult female is grey with a pale throat and fine streaking on the underparts.

Their breeding habitat is open or semi-open country across most of North America. This bird lays its eggs in the nests of other small passerines, particularly those that build cup nests, such as the Yellow Warbler. The young cowbird is fed by its foster parents at the expense of their own young.

They are permanent residents in the southern parts of their range; northern birds migrate to the southern United States and Mexico. They often travel in flocks, sometimes mixed with Red-winged Blackbirds or European Starlings.

These birds forage on the ground; often following grazing animals such as horses and cowss to catch insects stirred up by the larger animals. They mainly eat seeds and insects.

At one time, these birds followed the bison herds across the prairies. Their parasitic nesting behaviour complimented this nomadic lifestyle. Their numbers expanded with the clearing of forested areas and the introduction of new grazing animals by settlers across North America.

Over 140 different species of bird are known to have raised young cowbirds. If the cowbird egg is noticed, the intended victim may simply build a new layer over the bottom of the original nest.