The cowbird is a species classified as a "brood parasite," laying its eggs in the nest of other birds. The cowbird eggs hatch earlier, allowing those chicks an advantage against the host species' real young.
The cowbird lives across the entire United States and well into Canada. In its northernmost range, it only remains in the spring and summer before heading south to the southern states and Mexico for winter.
The preferred habitat is in an agricultural landscape that borders open woods. The cowbird will shun deeply forested areas of conifers or deciduous trees.
While the cowbird can reside in a prairie or grassland environment, such a region does not afford the luxury of a high perch from which the females can watch for nests to lay their eggs in.
Forests broken up by meadows and fields, known as fragmented forests, make ideal habitats for cowbirds. The birds take advantage of the trees at the edges to search for a host nest and eat the insects in the open areas.
Cowbirds would follow the huge herds of bison across America and gobble up the insects the large beasts stirred up. The development of the eastern portion of the nation allowed the cowbird to expand its range in that direction.