Brown-headed Cowbird females can lay 36 eggs in a season. Over 140 different species of birds are known to have raised young cowbirds. Host parents may sometimes notice the cowbird egg. Different species react in different ways. Gray Catbirds destroy the egg by pecking it. Some species may simply build a new layer over the bottom of the original nest. Brown-headed cowbird nestlings are sometimes expelled from the nest. This rejection, however, may trigger a "mafia" reaction, according to a study by the Florida Museum of Natural History.[1] When the parasitic egg was removed from the host nest, the cowbird returned to ransack the nest about 56% of the time. 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.
