"WHERE'S THE BEEF" AND "MAFIA BEHAVIOR"

MALE BROWN-HEADED COWBIRD 
(THE FEMALE IS ALL BROWN)

The brown-headed cowbird (Molothrus ater) of North America was not so named because it bore any resemblance to a moo-cow or because it was udderly fascinating. Instead, the bovine-related sobriquet was bestowed upon it because it enjoys following cattle, bison, and other large critters around and feasting upon the insects stirred up by the herd. 

Stalking a bunch of ungulates can result in you having a lousy home life if you are a bird. It is hard to raise a passel of young'uns in a nest if your food source has wandered off twenty miles away. In order to get around this predicament, cowbirds have evolved to be brood parasites. In other words, they allow other species of birds to take care of their eggs and fledglings. 

The female cowbird usually just lays one of her many eggs in each host's nest. In case the host bird knows how to count, mama cowbird will also usually remove one of the host's eggs so that the total number of eggs remains the same. 

The host mother bird will feed the cowbird young along with her own. However, the cowbird usually hatches and starts growing prior to its step-siblings and will thus have an advantage competing for food from the mother. If there is enough victuals for everyone, the young cowbird will allow its nestmates to dine; however, if resources are scarce, it will smother the other hatchlings or push them out of the nest. 

The brown-headed cowbird species is known to parasitize over 221 other types of birds. However, a specific mother cowbird will usually lay her eggs in the nests of the same species of bird which raised her. The coloration and appearance of cowbird eggs matches those of many host species. 

Before Ms. Cowbird hits the cattle trail again, she will often check back on each host nest where she left an egg. If the host mother has not molested the egg and it is still there, the mother cowbird will happily go on her way. However, if the host mother has detected that the egg is not hers and has removed or destroyed it, mama cowbird may do the avian equivalent of going medieval with a blowtorch and pliers and destroy the host's nest, eggs, and fledglings. This reaction is called by ornithologists "Mafia behavior," and learned guys (not to be confused with "wise guys") believe that Mafia behavior is an evolutionary trick which removes potentially non-cooperative hosts from the gene pool and encourages the natural selection of wimpy hosts who will do whatever the cowbird wants. 

Our friends in Europe should not feel jealous by virtue of the fact that they do not dwell in the presence of brown-headed cowbirds. They have their own version of brood parasites in the form of various species of cuckoos.