The Common Cuckoo (Cuculus canorus) (formerly European Cuckoo) is a member of the cuckoo order of birds, the Cuculiformes, which also includes the roadrunners, the anis, the coucals, and the Hoatzin.

The cuckoo group gets its English and scientific names from the call of the male Common Cuckoo, usually given from an open perch, goo-ko. The female has a loud bubbling call.

The cuckoo is a widespread summer migrant to Europe and Asia, and winters in Africa. It is a brood parasite, which lays its eggs in the nests of other bird species, particularly of Dunnocks, Meadow Pipits, and Reed Warblers.

This cuckoo is a greyish bird with a slender body, long tail and strong legs. The females only are sometimes brown, the "hepatic"? phase. This is a reference to the liver-like colour of the female plumage in this phase, and not to hepatic physiology. It looks like a small bird of prey in flight, although the wings stay below the horizontal. Its food is insects, with hairy caterpillars, which are distasteful to many birds, being a speciality. It is a bird of open land.

Brood parasite behaviour

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. At 14 days old, the Cuckoo chicks are about 3 times the size of the adult Reed Warblers. The numerous and rapid hunger calls of the single cuckoo chick, 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.

Cuckoo chicks methodically evict 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. Once the Reed Warbler chicks are out of the nest, the parents completely ignore them.

The combination of behaviour and anatomical adaptation of the common cuckoo was first described by Edward Jenner, who was elected as Fellow of the Royal Society in 1788 for this work. This was before he developed vaccination.

Egg colour

Female Cuckoos are divided into gentes, that is 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 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).

Legends about the Cuckoo

In Europe, hearing the call of the Cuckoo is regarded as the first harbinger of spring. Some local legends and traditions are based on this:

• In England and Wales, The Times newspaper prints correspondence every year reporting the first calls, usually around 14 April. The same thing happens in Asturias where numerous proverbs talk about the Cuckoo as a herald of spring, and where the local newspapers talk about it every year.
• In Russia, there's a popular belief that a cuckoo can predict how many more years a person will live. If a person hears a cuckoo in the woods, he or she usually asks "Cuckoo, cuckoo, how long will I live?". It is believed that a person will live as many years as a cuckoo cuckooed.
• In a similar way, the same beliefs are found in the traditional culture of Asturias, where people asks the cuckoo about their wedding day or how many years one will live, saying rhyming magical prayers like: "Cuquiellu, barbiellu, barbes d'escoba: ¿Cuántos años hai d'equí a la mio boda?" ("Cuckoo, cuckoo, beard of a broom, when will I get married?") and "Cuquiellu marmiellu, rau de perru, ¿Cuántos años hai d'equí al mio entierru?" ("Cuckoo, cuckoo, tail of a dog, how long until I'm buried?")
• In some regions of France, Romania and the Basque Country, a legend says that if someone has money in the pocket when they hear the first Cuckoo of the year, they will be rich the whole year.

Derivatives in the language

The word "cuckold" derives from the Cuckoo's practice of tricking other birds into raising its young.
The word "coccyx" derives from Greek kokkyx ("cuckoo") from the bone resemblance to a cuckoo's beak.

Genealogical

Cuckoo is a rare family name with origins believed to date back to 16th Century France. The Cuckoo name is now spread across most of the English speaking world with a concentration in England.