Numerous birds of the family Cuculidae (order Cuculiformes). The name usually designates some 60 arboreal members of the subfamilies Cuculinae and Phaenicophaeinae. In western Europe “cuckoo,” without modifiers, refers to the most common local form, elsewhere called the common, or European, cuckoo (Cuculus canorus). Many cuckoos have specialized names, such as ani, coua, coucal, guira, and roadrunner. Members of the subfamily Neomorphinae are called ground cuckoos. The family Cuculidae is worldwide, found in temperate and tropical regions but is most diverse in the Old World tropics. Cuculids tend to be shy inhabitants of thick vegetation, more often heard than seen. Many species are named for the sounds they make—e.g., brain-fever bird (a hawk cuckoo, Cuculus varius), koel (Eudynamys scolopacea), and cuckoo itself, the latter two names being imitations of the bird’s song.