# UKBirds

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## Common Cuckoo

### Cuculus canorus

The Common Cuckoo (formerly European Cuckoo) is a member of the cuckoo order of birds, Cuculiformes, which includes the roadrunners, the anis and the coucals.
This species is a widespread summer migrant to Europe and Asia, and winters in Africa. It is a brood parasite, which means it lays eggs in the nests of other bird species, particularly of Dunnocks, Meadow Pipits, and Eurasian Reed Warblers.
The Common Cuckoo is 32-34 centimetres (13-13 in) long from bill to tail (with a tail of 13-15 centimetres (5.1-5.9 in) and a wingspan of 55-60 centimetres (22-24 in). 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 (4.6 oz) and females 110 grams (3.9 oz). 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, goo-ko, is usually given from an open perch. 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.. The song starts as a descending minor third early in the year in April, and the interval gets wider, through a major third to a fourth as the season progresses, and in June the cuckoo "forgets its tune" and may make other calls such as ascending intervals. Also the cuckoo seems to have a form of absolute pitch as it tends to sing in the key of C.