The Screaming cowbird is a common bird throughout the Gran Chaco, as well as in Uruguay and other nearby areas. It is, beside the cuckoos, one of the more well-known and well-studied brood parasites. It specializes in another common bird species in Gran Chaco, the Grayish baywing (Agelaioides badius) [see image above]. The Screaming cowbird often lays an egg in the nest of this species, before the owners themselves have started laying. Research has shown that the Grayish baywing can recognize the eggs of the cowbird, and pushes them out of the nest and then lay their own. If the alien egg has been added later, the baywing can empty the whole nest and lay a new round of eggs. This behavior protects it against 75% of all attacks. But the story does not end here. Naturally, some eggs are not detected. When the intrusive chick is hatched, it looks slightly different from the others in the nest. But, after just a few days, it looks almost identical - and sounds the same - as their step-siblings. This is an example of 'mimicry' (imitation, adaptation). But the alien chicks scream somewhat higher than the original broodand succeed in getting enough to eat even when the food supply is scarce. For a long time, researchers believed that these two species were closely related. But DNA-analysis has shown that they are not close relatives.