The cowbird is a brood parasite that lays its eggs in the nests of other birds. Molothrus ater, the brown-headed cowbird, measures seven and one half inches long. The male has a metallic blackish-green body, dark brown head with a finch like bill. The female is grayish-brown with slight streaking. Molothrus aeneus, the bronzed cowbird, is six to nine inches long, the male sporting a black body with a bronze sheen, has a larger bill than that of the brown-headed cow bird, and has a red eye. Females' plumage is gray and she also has a red eye. Cowbirds are a gregarious species that is often seen mixed with blackbirds. Due to the female and juveniles dull streaked plumage and small size they can be often be mistaken for a House Finch or Sparrow. Cowbirds do not build their own nests or even raise their own young. The female, who mates several times in the season, May through August, is capable of laying one egg per day at the peak of the breeding season which may translate into 30-40 nests parasitized. She finds a nest where eggs have already been laid and often removes one of foe eggs and replaces it with her own. The young cowbird is usually the first egg to hatch, larger than the other birds, therefore exhausting the "host" parents for its feeding routine and can crowd the nestlings out of the nest, perishing them in the process.

Sheri Williamson, Southeastern Arizona Bird Observatory (SABO), Bisbee, suggests keeping cowbirds from hanging around the yard by taking down bird feeders during the breeding season or switching over to black oil sunflower seeds which cowbirds seem to dislike.

Sources: SABO, (520)432-1388, e-mail: sabo@SABO.org; Website: www.sabo.org, Smithsonian Migratory Bird Center -Fact Sheet No. 3, Gulfs Field Guide Series - A Field Guide to Birds of the Desert Southwest, Barbara L. Davis.