The Brown-headed Cowbird: North America's avian brood parasite

There are five species of parasitic cowbirds (Molothrus) and the Brown-headed Cowbird (M. ater) is the only widespread species in North America. The Brown-headed Cowbird is a host generalist and is typically found in open habitats and forest edges. The cowbirds are of a more recent origin than many other brood parasites and perhaps as a result, cowbird adaptations for parasitism and their hosts' counter-adaptations to thwart parasitism do not appear as sophisticated as those of other brood parasite-host systems. Because of its generalist nature, the cowbird has the potential to negatively impact endangered host species whose populations are limited due to anthropogenic habitat loss. As a consequence, the Brown-headed Cowbird is one of the few brood parasitic species that is the subject of control programs to limit its effects on such hosts.