The Common Cuckoo is a dove-sized bird, 32–34 centimetres (13–13 in) long (tail 13–15 cm) and wingspan 55–60 cm. It is greyish with a slender body and long tail and could be mistaken as a falcon in flight. There is also a rufous colour phase which occurs occasionally in adult females but more often in juveniles.
The cuckoo family gets its common name and genus name by onomatopoeia for the call of the male Common Cuckoo, usually given from an open perch, goo-ko. During the breeding season the male typically gives this call with intervals of 1–1.5 seconds, in groups of 10–20 with a rest of a few seconds between groups. The female has a loud bubbling call.
Distribution and habitatEdit
Essentially a bird of open land, the common cuckoo is a widespread summer migrant to Europe and Asia, and winters in Africa. In Britain these birds favor reedbeds, as many small warblers nest there.
Food and feedingEdit
The common cuckoo's diet consists of insects, with hairy caterpillars, which are distasteful to many birds, being a speciality of preference. It also occasionally eats eggs and chicks.
At the appropriate moment, the hen cuckoo flies down to the Reed Warblers' nest, pushes one Reed Warbler egg out of the nest, lays an egg and flies off. The whole process is achieved in only about 10 seconds.
A cuckoo chick methodically evicts all host progeny from host nests. It is a much larger bird than its hosts, and needs to monopolise the food supplied by the parents. The Cuckoo chick will roll the other eggs out of the nest by pushing them with its back over the edge. If the Reed Warbler's eggs hatch before the Cuckoo's egg, the Cuckoo chick will push the other chicks out of the nest in a similar way.
At 14 days old, the Cuckoo chicks are about three times the size of the adult Reed Warblers. The numerous and rapid hunger calls of the single cuckoo chick (which perfectly mimic the cries of a whole brood of warbler chicks), and to a lesser extent its coloured gape, encourage the host parents to bring more food.
Cuckoo chicks fledge after about 20–21 days after hatching, which is about twice as long as for Reed Warblers. If the hen cuckoo is out-of-phase with a clutch of Reed Warbler eggs, she will eat them all so that the hosts are forced to start another brood.
Female Cuckoos are divided into gentes - populations favouring a particular host species' nest and laying eggs which match those of that species in colour and pattern. The colour pattern is inherited from the female only, suggesting that it is carried on the sex-determining W chromosome (females are WZ, males ZZ). It is notable that most non-parasitic cuckoos lay white eggs, like most non-passerines other than ground nesters. The exception is in the case of the Dunnock, where the Common Cuckoo's egg has no resemblance to its hosts' blue eggs. This is thought to be because the Dunnock is a recent host, and has not yet acquired the ability to distinguish eggs. Male Cuckoos breed with females without regard to gens. This results in gene flow between the gentes and maintains a common gene pool for the species (except for the genes on the W chromosome)