Breeding pairs: 16,000
Adult male cuckoos have slate-grey upperparts, including the long, pointed wings. The tail is dark brown with white spots and tips, and black bars. The underparts are pale grey with dark grey and black heavy bars. The breast is pale slate-grey and the undertail feathers are black with white spots and edges.
The head is grey, the slightly curved bill is yellow with a black tip, the eyes are yellow-brown to orange with a yellow eye-ring, and the legs and feet are orange-yellow.
The female cuckoo is similar but the upper breast may be rufous instead of grey.
Juveniles have pale brown upperparts, with heavy black bars, and white tipped feathers. The tail has black bars. The underparts are white with fine, dark grey bars, and the eyes are dark brown with a yellow eye-ring. They have a white patch on their nape.
Cuckoos are brood parasites which means they lay their eggs in other birds’ nests, most often dunnocks’ and robins’ nests, and they leave the host birds to incubate and rear their young.
Female cuckoos lay their eggs with similar markings to the host bird’s eggs. The eggs are incubated for 11-12 days.
When the chicks hatch, they instinctively push the other eggs and nestlings out of the nest and they are then fed with the food brought back by the unsuspecting surrogate parents.
Baby cuckoos fledge after 17-21 days.
Cuckoos eat insects; mainly hairy caterpillars, beetles and ants but also dragonflies, crickets and mayflies.
Adult cuckoos arrive in the UK in late March and April and leave for Africa in July with juveniles leaving a month later.
They can be seen throughout the UK but are mostly found in southern and central England.
The common cuckoo is the only member of the family that calls cuckoo-cuckoo-cuckoo.