|Male Common Cuckoo (Cuculus canorus)|
Nearly 20, see text
- Sulawesi Cuckoo or Sulawesi Hawk-cuckoo, Cuculus crassirostris
- Large Hawk-Cuckoo, Cuculus sparverioides
- Dark Hawk-Cuckoo, Cuculus (sparverioides) bocki
- Common Hawk-Cuckoo, Cuculus varius
- Moustached Hawk-Cuckoo, Cuculus vagans
- Hodgson's Hawk-Cuckoo, Cuculus fugax
- Malaysian Hawk-Cuckoo, Cucuclus (fugax) fugax
- Hodgson's Hawk-Cuckoo, Cuculus (fugax) nisicolor
- Rufous Hawk-Cuckoo, Cuculus (fugax) hyperythrus
- Philippine Hawk-Cuckoo, Cuculus pectoralis
- Red-chested Cuckoo, Cuculus solitarius
- Black Cuckoo, Cuculus clamosus
- Indian Cuckoo, Cuculus micropterus
- Common Cuckoo, Cuculus canorus
- African Cuckoo, Cuculus gularis
- Himalayan Cuckoo, Cuculus saturatus
- Oriental Cuckoo, Cuculus optatus (formerly horsfieldi')
- Sunda Cuckoo, Cuculus lepidus
- Lesser Cuckoo, Cuculus poliocephalus
- Madagascar Cuckoo, Cuculus rochii
- Pallid Cuckoo, Cuculus pallidus
The hawk-cuckoos are sometimes placed in a separate genus, Hierococcyx, while the Pallid Cuckoo may belong in Cacomantis.
These are vocal species, with persistent and loud calls. They feed on large insects, with hairy caterpillars, which are distasteful to many birds, being a speciality. One or two species will also take some fruit.
Cuculus cuckoos are brood parasites, that is, they lay a single egg in the nests of various passerine hosts. The best-known example is the European Common Cuckoo. The female cuckoo in each case replaces one of the host’s eggs with one of her own. The cuckoo egg hatches earlier than the host’s, and the chick grows faster; in most cases the cuckoo chick evicts the eggs or young of the host species.
Cuculus species lay coloured eggs to match those of their passerine hosts. Female cuckoos specialise in a particular host species (generally the species that raised them) and lay eggs that closely resemble the eggs of that host.
A species may consist of several gentes, with each gens specialising in a particular host. There is some evidence that the gentes are genetically different from one another though other authorities state that as female cuckoos mate with males of any gens, genes flow between gentes.