Cowbird

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Cowbirds

Female M. ater

Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Passeriformes
Family:	Icteridae
Genus:	Molothrus Swainson, 1832

Species

Cowbirds are birds belonging to the genus Molothrus in the family Icteridae. They are brood parasitic New World birds which are unrelated to the Old World cuckoos, one of which, the Common Cuckoo is the best-known brood parasitic bird.

This family includes five species of cowbirds that form the natural genus Molothrus. This has been determined by phylogenetic analyses of mitochondrial DNA sequences (Lanyon 1992, Johnson and Lanyon 1999, Lanyon and Omland 1999, in Lowther, 2004).

The genus Molothrus includes:

Screaming Cowbird, Molothrus rufoaxillaris
Giant Cowbird, Molothrus oryzivorus (formerly in Scaphidura)
Bronzed Cowbird, Molothrus aeneus
Shiny Cowbird, Molothrus bonariensis
Brown-headed Cowbird, Molothrus ater

The non-brood parasitic Bay-winged Cowbird was formerly placed here; it is now Agelaioides badius.

These birds feed on insects, including the large numbers that may be stirred up by cattle. In order for the birds to remain mobile and stay with the herd, they have adapted by laying their eggs in other birds' nests. The cowbird will watch for when its host lays eggs, and when the nest is left unattended, the female will come in and lay its own eggs.

The cowbird eggs do not look much different from the hosts' eggs, and the host will normally incubate the eggs. The cowbird chicks grow quickly, and may consume most of the food the host brings. If starvation does not kill the other birds, in some species the cowbird will use its large size to push the other chicks out of the nest. The Giant Cowbird does not appear to harm its host oropendola or cacique chicks.