Brown-headed CowbirdMolothrus ater

adult male
Rick and Nora Bowers/VIREO
adult female
Rick and Nora Bowers/VIREO
Rick and Nora Bowers/VIREO
adult male
Rob & Ann Simpson/VIREO
nest with 3 Veery eggs and 1 cowbird egg
Michael Patrikeev/VIREO
Brown-headed Cowbird
Brown-headed Cowbird


6-8" (15-20 cm). Male black with glossy brown head; female plain gray-brown. Both have a finch-like bill.


Squeaky gurgle. Call is check or a rattle.


whistle call variants
whistles, chatter, and flight
male song
female chatter
male song and whistle call
male songs & female chatter (duets)


Agricultural land, fields, woodland edges, and suburban areas.


Breeds from British Columbia, central Saskatchewan, central Ontario, Quebec, and Newfoundland southward throughout United States except extreme Southeast and Florida. Winters in central and southern part of breeding range as well as in Florida.


Cowbirds are brood parasites and promiscuous; no pair bond exists. In late spring the female cowbird and several suitors move into the woods. The males sit upright on treetops, uttering sharp whistles, while the female searches for nests in which to lay her eggs. Upon choosing a nest, she removes one egg of the host's clutch, and deposits one of her own in its place. Unlike parasitic Old World cuckoos, which lay eggs closely resembling those of a host species, cowbirds lay eggs in the nests of more than 200 other species, most smaller than themselves. Some host species eject the unwanted egg, others lay down a mew nest lining over it, but most rear the young cowbird as one of their own. The young cowbird grows quickly at the expense of the young of the host, pushing them out of the nest or taking most of the food. It has been suggested that cowbirds became parasitic because they followed roving herds of bison and had no time to stop to nest.


4 or 5 white eggs, lightly speckled with brown, laid one at a time in the nests of other songbirds.

Similar Species

adult, breeding

European Starling

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