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A cuckoo is a bird in the family Cuculidae, which contains a broad cross-section of bird species found in both the Old and New World. These birds are particularly famous for their calls, which classically consist of two notes, although many cuckoo species can make additional noises, which often sound quite plaintive and haunting. Some members of the cuckoo family are also brood parasites, laying eggs in the nest of other birds to trick them into raising their young.
A number of traits can be used to identify a member of the cuckoo family. These birds tend to have very slender bodies, with long tails and stocky legs, and many have crests of their heads. The plumage of a cuckoo can vary, with many birds being grayish to brown in color, sometimes with patches of bright spots. These birds have what are known as zygodactyl toes, meaning that two toes face forward, and two toes face backward; this trait leads cuckoos to be classified as “near passerine birds.”
Cuckoo habitats vary widely. Some species prefer to live, nest, and hunt on the ground, while others fly and perch, building nests in trees. Cuckoos can be found in harsh desert environments, and lush forests, and many are quite adaptable, displaying a remarkable ability to cope with environmental changes. The vast majority of the birds are insectivorous, using their stout beaks to crush their prey before swallowing, and some cuckoos even prepare their food by scraping it across rocks and bark to remove unappetizing spines or hair.
Although the cuckoo is famous as a brood parasite, relatively few cuckoo species actually demonstrate parasitism. The vast majority prefer to nest and raise their own young. Among species which have evolved as brood parasites, the eggs are often similar in color and size to those of specific bird species, indicating that the birds have evolved to take advantage of particular birds. Cuckoo eggs usually hatch first, and the chick uses its larger size to crowd out the other hatchlings.
These birds are a topic of some discussion and debate among ornithologists. Several cuckoo species have proved difficult to classify, and some attempts have been made to sequence the genetics of the cuckoo in an attempt to unravel the complicated biological history of these birds. Cuckoos also display such a wide range of behaviors and vocalizations that the Cuculidae family is actually split up into a number of subfamilies, representing the clear differences between individual members of this avian family.