Brow-headed Cowbird

Description:

"A female cowbird lays her eggs in the nests of other species, which then raise her young." Stokes book. "It is a small brood parasitic icterid of temperate to subtropical North America. They are permanent residents in the southern parts of their range; northern birds migrate to the southern United States and Mexico in winter, returning to their summer habitat around March or April.[1] They resemble New World orioles in general shape but have a finch-like head and beak. The adult male is mainly iridescent black with a brown head while the adult female is grey with a pale throat and fine streaking on the underparts." Wikipedia

Habitat:

They occur in open or semi-open country and often travel in flocks, sometimes mixed with Red-winged Blackbirds (particularly in spring) and Bobolinks (particularly in fall), as well as Common Grackle or European Starlings.[1] These birds forage on the ground, often following grazing animals such as horses and cows to catch insects stirred up by the larger animals. They mainly eat seeds and insects. Before European settlement, the Brown-headed Cowbird followed bison herds across the prairies. Their parasitic nesting behaviour complemented this nomadic lifestyle. Their numbers expanded with the clearing of forested areas and the introduction of new grazing animals by settlers across North America. Brown-headed Cowbirds are now commonly seen at suburban birdfeeders.

Notes:

Read the Wikipage on this bird. It is a great read on parasitic nesting and habits. "It seems that Brown-headed Cowbirds periodically check on their eggs and young after they have deposited them. Removal of the parasitic egg may trigger a retaliatory reaction termed "mafia behavior". According to a study by the Florida Museum of Natural History published in 1983, the cowbird returned to ransack the nests of a range of host species 56% of the time when their egg was removed. In addition, the cowbird also destroyed nests in a type of "farming behavior" to force the hosts to build new ones. The cowbirds then laid their eggs in the new nests 85% of the time.[7]" Wikipedia...the whole article is fascinating reading.