Cuckoo, one of a large, diverse family of birds found all over the world. In addition to cuckoos, the family includes several species of anis (black cuckoos) and the roadrunner. The song of the cuckoo has been the sign of spring in England and other parts of Europe for centuries. Many stories and songs have been written about the cuckoo, and its call is imitated by cuckoo clocks.

CuckoosCuckoos have feet with two toes pointing forward and two backward.

There are more than 125 species of cuckoos. Most of the species are found in the Eastern Hemisphere. All members of the cuckoo family have feet with two toes pointing forward and two backward. This foot structure allows the birds to climb on slender stems and to run swiftly over the ground.

The European cuckoo has become legendary for its habit of laying its eggs in the nests of other birds. The young cuckoo is much larger than the other nestlings and soon crowds the rightful occupants out of the nest. The foster parents, apparently mistaking it for one of their own, work frantically to feed the hungry young cuckoo with worms and insects. As soon as it is able to fly. the cuckoo leaves. Some birds will roof over their nest if they find a cuckoo egg in it. A new nest is built on top of the old and more eggs are laid.

American cuckoos make their own nests—messy structures built in dense thickets of shrubbery. The most common American species is the yellow-billed cuckoo, which is about 12 inches (30 cm) long. Its upper parts are gray-brown and its underparts white. The tail feathers are dark with white tips, and the bill is yellow. The bird is native to the eastern United States. The black-billed cuckoo is similar, but has a black bill. It ranges over much the same territory as the yellow-billed cuckoo, but is found as far west as the Rocky Mountains.

Cuckoos belong to the family Cuculidae. The European cuckoo is Cuculus canorus; the yellow-billed is Coccyzuz americanus; the black-billed, C. erythropthalmus.