The cuckoos are a family, Cuculidae, of near passerine birds. The order Cuculiformes, in addition to the cuckoos, also includes the turacos (family Musophagidae, sometimes treated as a separate order, Musophagiformes). Some zoologists and taxonomists have also included the unique Hoatzin in the Cuculiformes, but its taxonomy remains in dispute. The cuckoo family, in addition to those species named as such, also includes the roadrunners, koels, malkohas, couas, coucals and anis. The coucals and anis are sometimes separated as distinct families, the Centropodidae and Crotophagidae respectively.
The cuckoos are generally medium sized slender birds. The majority are arboreal, with a sizeable minority that are terrestrial. The family has a cosmopolitan distribution, with the majority of species being tropical. The temperate species are migratory. The cuckoos feed on insects, insect larvae and a variety of other animals, as well as fruit. Many species are brood parasites, laying their eggs in the nests of other species, but the majority of species raise their own young.