Today I saw a brown-headed cowbird looking for food with some sparrows. They are a bit larger than the sparrows, maybe by an inch or so; the male has a brown head, & a glossy black body, & the female is grayish-brown all over. Brown-headed cowbirds are North America’s most infamous brood parasite. They don’t build their own nests, incubate their own eggs, & rear their own chicks, instead, brown-headed cowbirds have a developed an alternative breeding strategy. The females use other birds as hosts – they lay their eggs in nests of other bird species and rely on those birds to incubate and raise their young. It has been discovered that brown-headed cowbirds have parasitized more than 220 host species, such as the black-capped vireo, blue-winged teal, & red-headed woodpecker. However, not all host birds make good parents – a number of birds will toss the cowbird eggs out of their nests upon finding them, because brown-headed cowbird eggs can look distinctly different from the eggs of their host species. Still, brown-headed cowbird chicks have been raised successfully by more than 150 host species (which is less than 3/4 of the birds they try to get to raise their young), & songbirds make up most of their hosts.