The adult birds usually have blue-grey head, breast and upperparts, and horizontal barring on the underparts and white spots and tips on the tail. However, the female also exists as a rare rufous "hepatic" morph, so instead of being grey it is red-brown. The eyes and legs are yellow and the slightly curved bill is horn-coloured.
In flight, the Cuckoo can be easily mistaken for a Sparrowhawk or Kestrel, because it has swept-back wings and long tail. However, Sparrowhawks do not have pointed wings like the Cuckoo, and the Kestrel is streaked and not barred on the underparts.
When perched, usually in the open at the top of a tree, the Cuckoo drops its wings below the level of its tail, as in the photograph. The best places to see Cuckoo are grassland, reed beds, and edges of woodland.
Juveniles are similar to the rufous female, but with a white patch on the nape.
An old rhyme describes the Cuckoo's time in Britain:
In April I open my bill
In May I sing night and day
In June I change my tune
In July far far I fly
In August away I must
| Scientific Name | Cuculus canorus |
| Length | 32-36 cm (13-14½") |
| Wing Span | 54-60 cm (21½-24") |
| Weight | 105-130 g (3¾-4¾ oz) |
| Breeding Pairs | 30000 |
| Present | Summer |
| Status | Red |
The female has a rich bubbling chuckle, but the male's call is the very familiar "cuckoo".
Generally, if you hear a Cuckoo singing you will probably not see it until it stops singing, which is when it flies away from its song post.
Caterpillars and other insects such as beetles and ants form the major part of the Cuckoo's diet. Many of the caterpillars are the hairy or brightly coloured poisonous ones, but their digestive system is specially adapted to cope with the hairs and toxins.
The female will also sometimes eat the eggs and nestlings of the host bird.
The Cuckoo is a brood parasite, it lays its eggs in other birds' nests and leaves the host birds to incubate and rear its young. Dunnocks, Robins and Meadow Pipits are frequent host birds. Each female Cuckoo specialises in using a particular host species and will lay eggs with similar markings to the host bird's eggs, and the young Cuckoo will imitate the begging calls of the host's chicks.
When the Cuckoo nestling hatches, it instinctively pushes the other eggs and nestlings out of the nest.
| Breeding Starts | Clutches | Eggs | Incubation (days) | Fledge (days) |
|---|---|---|---|---|
| late May | 1-25 | 1 | 11-12 | 17-21 |
They are a summer migrant, arriving around April and returning to central and southern Africa from mid-July to August. The juveniles follow in August and September.
Since the early 1980s, the numbers of Cuckoos has been in decline and this may be because the populations of some key host species, such as Dunnock and Meadow Pipit, have also declined. Consequently, the Cuckoo is now red list species.
