Cuckoo
Breeding

The cuckoos are an extremely diverse group of birds with regards to breeding systems. Most are monogamous, but exceptions exist. The anis and the guira cuckoo lay their eggs in communal nests, which are built by all members of the group. Incubation, brooding, and territorial defence duties are shared by all members of the group. Within these species, the anis breed as groups of monogamous pairs, but the guira cuckoos are not monogamous within the group, exhibiting a polygynandrous breeding system. This group nesting behaviour is not completely cooperative; females compete and may remove others' eggs when laying theirs. Eggs are usually only ejected early in the breeding season in the anis, but can be ejected at any time by guria cuckoos. Polyandry has been confirmed in the African black coucal and is suspected to occur in the other coucals, perhaps explaining the reversed sexual dimorphism in the group.

Most cuckoo species, including malkohas, couas, coucals, and roadrunners, and most other American cuckoos, build their own nests, although a large minority engages in brood parasitism (see below). Most of these species nest in trees or bushes, but the coucals lay their eggs in nests on the ground or in low shrubs. Though on some occasions nonparasitic cuckoos parasitize other species, the parent still helps feed the chick.

The nests of cuckoos vary in the same way as the breeding systems. The nests of malkohas and Asian ground cuckoos are shallow platforms of twigs, but those of coucals are globular or domed nests of grasses. The New World cuckoos build saucers or bowls in the case of the New World ground cuckoos.

Nonparasitic cuckoos, like most other nonpasserines, lay white eggs, but many of the parasitic species lay coloured eggs to match those of their passerine hosts.

The young of all species are altricial. Nonparasitic cuckoos leave the nest before they can fly, and some New World species have the shortest incubation periods among birds.
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