The cuckoos of the New World and some of those of the Old make their own nests in normal avian fashion. But a number of Old World species are social parasites, and their behavior has long been a subject of study and discussion. Specializations indicate that here perhaps we have the highest stages of social parasitism. Whereas the cowbird may grow up with nestmates that are the young of the foster parent, unless perchance it crowds them out or starves them if it is larger, the young cuckoo gets the rightful occupants of the nest on its back and throws them out of the nest to perish. EGGS LOOK ALIKE Another refinement in social parasitism by the European cuckoo is that apparently certain individuals, and apparently certain strains, lay their eggs only in the nests of certain host species. And these cuckoos' eggs resemble those of the particular species in whose nest the cuckoos' eggs are laid. For example, if certain cuckoos lay their eggs only in the nests of meadow pipits these cuckoos' eggs would resemble those of meadow pipits, while another group of cuckoos specializing in hedge-sparrows would have eggs resembling those of hedge-sparrows. Another oriental cuckoo has a color adaptation in the young. In southern Asia these cuckoos parasitize crows, and the nestling cuckoos have black feathers like the young crows; in the Australian area where the same species of cuckoo occurs it parasitizes grayish-brown honey eaters and the young are brown, more like the rightful nestlings. Both these resemblances apparently reduce the chances of the cuckoos' offspring being rejected by the foster parents. FISH EATS BIRD! [Illustration] It has become commonplace to hear about birds eating fish. The government gets out reports on the relation of fish-eating birds to fish abundance. The cries of commercial fisheries have caused inquiries to be instituted into the food of cormorants that were supposed to be eating the fish before they grew up enough for us to eat. The scarcity of salmon in some of our Northeastern streams has caused the allocation of biologists to study the predation of kingfisher and merganser on salmon fry and fingerlings. But fish get some of their own back by eating birds. It's not as spot news as the "man bites dog" angle, but it's certainly less widely known. To one who has fished for large-mouth black bass among the cypress trees and the bonnets of water hyacinth, and seen the bass strike savagely at surface lures as soon as they hit the surface, it comes as no surprise to find they strike at, and catch, such birds as Maryland yellow-throats that flutter across close to the surface of the water.