The most common brood parasite

Brown-headed cowbirds were so named because they follow herds of grazing animals, such as buffalo and later cows, eating the insects disturbed by the herd. But today cowbirds are best known for being “brood parasites.” They don’t build nests. Instead, they lay eggs—often dozens of eggs in a single summer—in the nests of other types of birds who then raise the cowbirds as their own. Cowbirds have to choose wisely though. Birds such as robins and brown thrashers often recognize and remove cowbird eggs from their nests. And even if birds don’t recognize the cowbird eggs, the young insect-eating cowbirds will not survive if the foster parents are seed-eaters like gold finches.