Jeewa was surprised to find an American redstart feeding such a big baby that looked nothing like the adult. It always comes as a surprise to find that we also have a parasitic bird here, just as there is in Europe (the Cuckoo). It is a common sight to find birds such as redstarts, yellow warblers, song sparrows, and others, feeding a very big baby, much bigger than the "parent" bird. Female cowbirds seek out the cup nests, such as those made by the above species, and typically will turf out the eggs already laid and lay her own. Some birds are better able to cope with this intrusion than others, and will either build another nest layer on top of the egg, or try to shove it over the side and lay their own.