Cuckoo  (Cuculus canorus)

A widespread summer visitor (3). Included in the Birds of Conservation Concern Amber List (medium conservation concern) (4) and protected at all times under the Wildlife and Countryside Act 1981 (5).

A well-known harbinger of spring, the arrival of the cuckoo in Britain is eagerly awaited each April (3). Adult males have bluish-grey upperparts and a white belly with dark barring. Females occur in two forms, one is similar to the male but the breast is buff coloured with dark barring; the other form is reddish brown, and often wholly covered with dark bars (2). Juveniles are slate-grey with touches of reddish-brown (2). The familiar call 'cuck-oo, cuck-oo' is imitated by the common name; later in the year females produce a 'bubbling' call (6).

Arrives in Britain during the second part of April from Africa south of the Sahara, and leaves in September (2). It is widespread in Britain and breeds throughout Europe, reaching as far east as Japan (3).

Occupies a broad variety of habitats, including all types of woodland, marshes, heaths and alpine areas (2).

The cuckoo is the only 'brood parasite' to breed in Britain (3). Individual females prefer certain foster birds, and lay eggs that closely mimic those of the foster species, 50 of which are known (3). A female will establish a territory encompassing a number of potential foster nests, and carefully observe activity, waiting until the nests are at the right stage. She then swiftly takes her chance, swooping down, ejecting an egg and laying one of her own (3). The unsuspecting host bird then incubates and feeds the impostor, who removes other eggs and young from the nest and often grows much larger than its foster parent (3). Female cuckoos usually lay fewer than 12 eggs in 12 different host nests each year (3). Cuckoos feed mainly on insects, spiders and worms (3).

The Breeding Bird Survey (BBS) has shown that the population of the cuckoo in Britain has declined steadily; this is thought to be due to a decrease in populations of key host species such as meadow pipit and dunnock (7), probably due to habitat-related factors (5).

No specific conservation action has been targeted at this species.

For more on British birds see the RSPB website:
http://www.rspb.org.uk
For more on this species see the RSPB's cuckoo information:
http://www.rspb.org.uk/birds/cuckoo/?page=c

Information authenticated by the RSPB:
http://www.rspb.org.uk/

1. National Biodiversity Network Species Dictionary (November 2002): http://www.nhm.ac.uk/nbn/
2. Mullarney, K., Svensson, L., Zetterstrom, D., & Grant, P.J. (1999) Collins Bird Guide. HarperCollins Publishers Ltd, London.
3. Gooders, J. (1982) Collins British Birds. William Collins Sons and Co Ltd, London.
4. RSPB (2003) The population status of birds in the UK: http://www.rspb.org.uk/Images/5_20625.pdf
5. RSPB (2003): Pers. comm
6. Greenoak, F. (1979) All the birds of the air. Book Club Associates, London.
7. BTO, Breeding Birds in the Wider Countryside (November 2002): http://www.bto.org/birdtrends2000/wcrcucko.htm