Common Cuckoo

Appearance

The Common Cuckoo is 32–34 centimetres long from bill to tail and a wingspan of 55–60 centimetres. The legs are short. It is greyish with a slender body and long tail and can be mistaken for a falcon in flight, where the wingbeats are regular. During the breeding season, Common Cuckoos often settle on an open perch with drooped wings and raised tail. There is a rufous colour phase, which occurs occasionally in adult females but more often in juveniles.

All adult males are slate-grey; the grey throat extends well down the bird's breast with a sharp demarcation to the barred underparts. The iris, orbital ring, the base of the bill and feet are yellow. Grey adult females have a pinkish-buff or buff background to the barring and neck sides, and sometimes small rufous spots on the median and greater coverts and the outer webs of the secondary feathers.

Rufous phase adult females have reddish-brown upperparts with dark grey or black bars. The black upperpart bars are narrower than the rufous bars, as opposed to rufous juvenile birds, where the black bars are broader.

Common Cuckoos in their first autumn have variable plumage. Some are have strongly-barred chestnut-brown upperparts, while others are plain grey. Rufous-brown birds have heavily-barred upperparts with some feathers edged with creamy-white. All have whitish edges to the upper wing-coverts and primaries. The secondaries and greater coverts have chestnut bars or spots. In spring, birds hatched in the previous year may retain some barred secondaries and wing-coverts. The most obvious identification features of juvenile Common Cuckoos are the white nape patch and white feather fringes.

Common Cuckoos moult twice a year: a partial moult in summer and a complete moult in winter. Males weigh around 130 grams and females 110 grams. The Common Cuckoo looks very similar to the Oriental Cuckoo, which is slightly shorter-winged on average.

A study using stuffed bird models found that small birds are less likely to approach Common Cuckoos that have barred underparts similar to the Eurasian Sparrowhawk, a predatory bird. Eurasian Reed Warblers were found more aggressive to cuckoos that looked less hawk-like, meaning that the resemblance to the hawk helps the cuckoo to access the nests of potential hosts.

The male's call, is 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

Essentially a bird of open land, the Common Cuckoo is a widespread summer migrant to Europe and Asia, and winters in Africa. Birds arrive in Europe in April and leave in September.

The Common Cuckoo has also occurred as a vagrant in countries including Barbados, the United States of America, Greenland, the Faroe Islands, Iceland, Indonesia, Palau, Seychelles, Taiwan and China.

Reproduction

The Common Cuckoo is a brood parasite; it lays its eggs in the nests of other birds. At the appropriate moment, the hen cuckoo flies down to the host's nest, pushes one egg out, lays an egg and flies off. The whole process takes about 10 seconds. A female may visit up to 50 nests during a breeding season. Common Cuckoos first breed at two years old.

More than 100 host species have been recorded: Meadow Pipit, Dunnock and Eurasian Reed Warbler are the most common hosts in northern Europe; Garden Warbler, Meadow Pipit, Pied Wagtail and European Robin in central Europe; Brambling and Common Redstart in Finland; and Great Reed Warbler in Hungary.

The egg measures 22 by 16 millimetres and weighs 3.2 grams, of which 7 % is shell. Research has shown that the female Common Cuckoo is able to keep its egg inside its body for an extra 24 hours before laying it in a host's nest. This means the cuckoo chick can hatch before the host's chicks do, and it can eject the unhatched eggs from the nest.

Scientists incubated Common Cuckoo eggs for 24 hours at the bird's body temperature of 40 °C, and examined the embryos, which were found "much more advanced" than those of other species studied. The idea of 'internal incubation' was first put forward in 1802 and 18th and 19th Century egg collectors had reported finding that cuckoo embryos were more advanced than those of the host species.

Food

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.

Cultural

In Europe, hearing the call of the Common Cuckoo is regarded as the first harbinger of spring. Many local legends and traditions are based on this. In Scotland, a number of Gowk Stones exist, sometimes associated with the arrival of the first cuckoo of spring. "Gowk" is an old name for the Common Cuckoo in northern Britain, derived from a harsh repeated ""gowk"" call the bird makes when excited.

The well-known cuckoo clock features a mechanical bird and is fitted with bellows and pipes that imitate the call of the Common Cuckoo.