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.

Morphology

The subfamily Cuculinae are the brood-parasitic cuckoos of the Old World. They tend to conform to the classic shape, with (usually) long tails, short legs, long narrow wings and an arboreal lifestyle. The largest species, the Channel-billed Cuckoo, also has the most outsized bill in the family, resembling that of a hornbill. The subfamily Phaenicophaeinae are the non-parasitic cuckoos of the Old World, and include the couas, malkohas, and ground-cuckoos. They are more terrestrial cuckoos, with strong and often long legs and short rounded wings. The subfamily typically has brighter plumage and brightly coloured bare skin around the eye. The coucals are another terrestrial subfamily of long tailed long legged and short winged cuckoos. They are large heavyset birds with the largest, the Greater Black Coucal, being around the same size as the Channel-billed Cuckoo. The subfamily Coccyzinae are arboreal and long tailed as well, with a number of large insular forms. The typical ground-cuckoos are similar to the Asian ground-cuckoos in being long legged and terrestrial, and includes the long billed roadrunner which can reach speeds of 30 km/h when chasing prey. The final subfamily are the atypical anis, which include the small clumsy anis and the larger gurias. The anis have massive bills and smooth glossy feathers.

Cuckoo genera differ in the number of primary wing feathers as below.

• Phaenicophaeus, Coccyzus, Piaya - 9
• Cuculus - 9 or 10
• Pachycoccyx, Clamator levaillantii, Centropus - 10
• Microdynamis, Eudynamys,Clamator glandarius - 11
• Some coucals - 12
• Scythrops novaehollandiae - 13