August’s Bird of the Month!

The handsome Brown-headed Cowbird (Molothrus ater) is a grassland and edge species, found from Saskatchewan and southern Canada through the lower 48 states and into northern Mexico, with a fascinating approach to rearing young: it doesn’t. These birds practice brood parasitism, the term used when one species of animal uses another species to raise its young. Historically, the Brown-headed Cowbird would follow bison herds as they traveled across the grasslands and prairies. Ornithologists believe that, due to their nomadic lifestyle, Brown-headed Cowbirds became brood parasites because they would not have time to make their own nests and raise their young before the bison moved on to a new area. The survival of the species depended on Brown-headed Cowbirds developing a reproductive adaptation: laying their eggs in other birds’ nests for the parents of the other species to incubate, hatch, and raise their young. Bison numbers declined drastically in the 1800s, but interestingly the cowbird population have not declined and have even increased in the last few decades. It seems as though this species evolves dramatically fast and adapts to the changes in landscape and environment. Where the cowbird used to lay eggs in grassland species’ nests, they now are laying their eggs in a lot of “backyard bird” nests. This Missouri native is often thought of as a pest because they parasitize declining species such as Eastern Bluebird. Brown-headed Cowbirds have been documented laying eggs in nests of 219 species, taking away much-needed resources from the host-species nestlings. These unique birds can live up to 17 years, and are about the size of a Northern Cardinal.

Photo Credit: Dan Getman

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