Brown-headed Cowbirds

Brown-headed CowbirdThe Brown-headed Cowbird (Molothrus ater) is a small icterid.

Distribution / Range

Brown-headed Cowbirds are permanent residents in the southern parts of their range, while the northern birds breed in open or semi-open country across most of North America and migrate to the southern United States and Mexico for the winter.

They often migrate in flocks, sometimes mixed with Red-winged Blackbirds or European Starlings.


Adults have a short finch-like bill and dark eyes. The adult male can be identified by his iridescent black plumage with a brown head. The adult female is mostly grey with a pale throat and fine streaking on the plumage below.

Diet / Feeding

Brown Cowbirds mostly eat seeds and insects, taken from the ground. They often follow grazing animals, such as horses, bisons, and cows, to catch insects they stirred up.

Brown-headed Cowbirds are now commonly seen at birdfeeders.

Nesting / Breeding

Brown-headed Cowbird females can produce 36 eggs in a season.

This brood parasite will deposit its eggs in the nests of other small passerines (perching birds), particularly those that build cup-like nests, such as the Yellow Warbler. The young cowbirds are then raised by the host parents. Over 140 different species of birds are known to have raised cowbirds. Host parents may notice the cowbird egg and some species may destroy the eggs (such as the Grey Catbirds), while others may simply build a new layer over the bottom of the original nest. Brown-headed cowbird nestlings are sometimes expelled from the nest.

Species Research by Sibylle Johnson

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