Cuckoo, a bird named from its coo coo cry, found both in the Old and the New World. The European cuckoos have the habit of laying their eggs in the nests of other birds—usually smaller birds than themselves. But this habit is not common to all members of the group, for a number of the cuckoos make nests. The two forms common in the northeastern United States are the yellow-billed and the black-billed cuckoos, birds with noticeably long tails, of an olive-brown color above and white below. They make a loose nest of twigs, and lay four or five eggs of a pale, greenish color. They destroy many injurious caterpillars, and one writer suggests they might well be called the caterpillar-bird. They are shy birds, and the call of the rain-crow, as they are commonly called, is better known than the bird itself. It is a series of tut-tuts, followed by cl-uck-chucks, and then a loud cow-cow-cow.