cuckoo, common name for members of the extensive avian family Cuculidae, including the ani and the roadrunner (Geococcyx californianus), widely distributed in temperate and tropical regions. Cuckoos are slender-bodied, long-tailed birds with medium to stout down-curved bills, pointed wings, short legs (except in the terrestrial species), and dull (usually grayish brown or rufous) plumage. They are generally insectivorous and arboreal.
Of the parasitic Old World cuckoos, the common European cuckoo, Cuculus canorus, is typical. The female visits the nests of smaller birds, selecting those whose eggs match hers in color, and replaces an egg of the host with one of her own; she usually lays four or five eggs, each at 48-hr intervals and each in a different nest. Because the female can retain an egg inside inside its body longer, leading to internal incubation, the embryo is more developed when the egg is laid. The young cuckoo, hatching earlier and being larger than its nest mates, displaces them from the nest and becomes the sole recipient of its foster parents' care.
Each species of Old World cuckoo has its own unique pattern of parasitism, and different species choose different host species for their eggs. The cuckoo is referred to in the Bible, by Aristotle and Pliny, in mythology, and in English poetry. Its nesting habits have given us the word cuckold, and its simple but musical song, which gives it its name, was used by Beethoven in his Pastoral Symphony and is also imitated in the cuckoo clock.
The American cuckoos look like attenuated pigeons; they are not parasitic and build flimsy nests of twigs. Typical are the black-billed and yellow-billed (Coccyzus americanus) cuckoos, known for their low, chuckling call notes. They frequent and breed at the edges of deciduous woodlands, either species tending the young of the other. These birds are valued as destroyers of harmful insects—particularly the tent caterpillar, which few other birds will eat. There are also western and southern species.
Most gregarious of the cuckoos are the anis of the American tropics. The groove-billed ani, from 12 to 14 in. (30–35 cm) long, has black plumage with a faint purple gloss. Anis nest colonially, several females together laying as many as 25 eggs in the same nest, and they may breed at any time of the year.
Of the ground cuckoos, the roadrunner, or chaparral cock, of the southwest deserts is best known. It feeds mostly on small snakes and lizards, which it pounds to death with its heavy bill and swallows headfirst. The roadrunner speeds over the ground at up to 15 mi (24.14 km) per hr with its long tail extended horizontally, its head down, and its ragged crest erect. Roadrunners are weak fliers and nonmigratory. They build coarse nests in thorny bushes; because they lay at intervals, both eggs and young may appear together in the nest.
Also included in the cuckoo family are the coucals, medium to large in size, slow-flying, mostly terrestrial birds of the tropics from Africa to Australia, e.g., the black concal, Centropus grilli. Cuckoos are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Cuculiformes, family Cuculidae.