If birds had post offices, posters of brown-headed cowbirds would be pinned to bulletin boards, and described as “fertile and dangerous.”
Cowbirds are notorious, more than any other American species, for laying eggs in the nests of other birds. Those eggs often hatch before those of the host species and the fledgling cowbirds crowd either the host eggs or young birds from the nest. The host parents are fueled by instincts to protect and feed any young within their nests and dutifully feed and raise the young cowbirds as their own.
Such parasitic behavior has been documented against at least 100 species of birds, including several that are on threatened or endangered species lists. In some areas biologists are cropping the cowbird population so they can’t continue to decimate host species.
Brown-headed cowbirds are native to most of Kansas and historically followed herds of bison around the prairie.