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brown-headed cowbird

brown-headed cowbird (Molothrus ater) [female]
Photo provided by SteveByland/

brown-headed cowbird (Molothrus ater) [male]
Photo provided by SteveByland/

Features and Behaviors

The brown-headed cowbird averages seven inches in length (tail tip to bill tip in preserved specimen). It has a short, chunky bill. The male has black feathers on the body with brown head feathers. The female has gray feathers all over. Young birds are lighter gray than the female and have streaked feathers on the breast. Young males during molting in the summer may show both brown and black feathers.

The brown-headed cowbird is a common migrant and summer resident throughout Illinois and a common winter resident in southern Illinois. It lives in all habitats but is especially often found in forest edges, fence rows and shrubs, where its “glug-glug-gleeee” song may be heard. Spring migrants begin arriving in Illinois in February. Eggs are produced from April through July. The brown-headed cowbird is a brood parasite. It does not build its own nest but lays its eggs in the nests of other birds, generally woodland-nesting species. The female cowbird lays one egg per day at dawn until her full clutch of about six eggs is produced. The eggs may be placed in as many different nests as there are eggs. The egg is white with brown markings. A female cowbird may produce several clutches, laying as many as 30 eggs in a summer. The advantage to the cowbird is that it doesn’t have to raise its young. It usually uses the nest of a bird species smaller than itself. The egg or eggs it leaves in the nest are bigger than those of the host, hatch faster and get the most attention from the adult. At least 61 species of Illinois-nesting birds have been parasitized by the cowbird. Some accept the egg(s) and raise them as their own; others remove them from the nest; others may desert the nest; or others may build a new nest on top of the one containing the cowbird egg. Brown-headed cowbirds form huge roosts in fall and winter. Feeding in open areas around cattle and in short-grass fields the cowbird eats insects, fruits, seeds and grains.

Illinois Range


Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Icteridae

Illinois Status: common, native