The Giant Cowbird, Molothrus oryzivorus, is a large perching bird of the family Icteridae. It breeds from southern Mexico south to northern Argentina, and on Trinidad and Tobago. It is found in open woodland and cultivated areas with large trees, but is also the only cowbird that is found in deep forest.
The male Giant Cowbird is 14 inches long and weighs 6.35 ounces. The bird is shiny black with a long tail, long bill, small head and a neck ruff which is expanded in display. The female cowbird is about 11inches long and weighs 4.75 ounces. She is less iridescent than the male and she has no neck ruff. Young birds are more similar to the adult male but are a darker brown with a pale bill.
Like other cowbirds, the Giant Cowbird is a brood parasite. It lays its eggs in the nests of other birds. Several cowbird eggs may be laid in a single host nest. The eggs are either whitish and unspotted or pale blue or green with dark spots. It has been theorized that the Giant Cowbird chick is beneficial to its host’s chicks by eating parasitic flies in the nest.
This gregarious bird feeds mainly on insects and some seeds, including rice, and forages on the ground or in trees. It rarely perches on cattle, unlike some of its relatives, but in Brazil it will ride on Capybaras as it removes horse flies.