Late laying by a Brown-headed cowbird, in an American goldfinch nest

Nest desertion by blue-gray gnatcatchers in association with brown-headed cowbird parasitism

The blue-gray gnatcatcher, Polioptila caerulea, is one of the smallest regular hosts of the brown-headed cowbird, Molothrus ater. Gnatcatchers typically raise none of their own young when parasitized, yet anti-parasite behaviours have not been reported. A blue-gray gnatcatcher population in which pairs often desert nests when parasitized by cowbirds was studied to examine the success of a deser...

Male Brown-headed Cowbird Attacks and Kills a Nestling

I observed a male Brown-headed Cowbird (Molothrus ater) attack and kill a nestling of an unidentified passerine in a grassland field in Day County, South Dakota, in June 2000. The killing or removal of nestlings by female cowbirds has been reported by others, but this behavior has not been documented previously in male cowbirds. Received 8 October 2002, accepted 3 March 2003. Female Brown-heade...

FEMALE INFLUENCE IN THE BROWN-HEADED COWBIRD (Molothrus ater): AN INVESTIGATION OF EMERGING SOCIAL ECOLOGIES

High offspring survival of the brown-headed cowbird in an invaded habitat

The brood parasitic brown-headed cowbird (Molothrus ater) is considered an important threat to bird conservation in North America because it reduces the reproduction of its numerous host species. Prior to the colonisation of America by Europeans, the cowbird was largely confined to the North American prairie region, but it has since invaded forests and other habitats and is now one of the conti...

Mite-filled cyst on a Brown-headed Cowbird (Molothrus ater) in Florida, USA.

A large, partly pedunculated mass on the scapular area of a wild-caught captive Brown-headed Cowbird (Molothrus ater) consisted of a multiloculated keratin cyst inhabited by a new species of harpirhynchid mite (Harpirhynchus quasimodo). The mass did not interfere with flight or behavior. This is the first record of such an infestation of cowbirds in Florida.