© Copyright: Images: Jari Peltomäki, M. & W. von Wright: Svenska fåglar (Kansalliskirjasto, The National Library of Finland). Recording: Jan-Erik Bruun. All rights reserved.
- Name also: Common Cuckoo, European Cuckoo
- Family: Cuckoos – Cuculidae
- Appearance: Grey or brown in colouring. Tail long, wings sharp-ended. In flight looks hawk-like, but wings held below the horizontal from the body.
- Size: Length 32–36 cm, wingspan 54–60 cm, weight 80–160 g.
- Nest: Parasitically lays its eggs in the nests of other birds (passerines, notably Redstart, Meadow Pipit, Pied Wagtail, Dunnock, Brambling). The Cuckoo fledgling ejects the eggs or fledglings of its foster parents from the nest.
- Breeding: Eggs laid from mid May to early July, every two or three days. Cuckoo eggs take about 12 days to hatch. Fledglings remain in nest for 18–23 days, and continue to be fed by their unwitting foster parents for about a further three weeks.
- Distribution: May be found in a wide range of habitats including all kinds of forests, also in urban areas and coastal islands. Finnish population estimated at 100,000–120,000 pairs.
- Migration: Leaves Finland between late July and early October, returning from late April. Winters in tropical Africa.
- Diet: Various insects, particularly hairy caterpillars.
- Calls: Familiar “cuck-koo” call.
Cuckoos are quite similar to Sparrowhawks in appearance, but in flight they beat their sharp-ended wings rapidly and evenly with shallow wingbeats below the horizontal from the body. Their heads also have an elongated tapering profile in flight silhouette, and their beaks are straight (not hooked like a hawk’s beak). Their long tails are spotted (not barred like Sparrowhawk) and round-ended. Cuckoos have bluish grey upper parts and their underparts are barred with dark and light crosswise stripes.
The sexes are quite similar, though females have a rust-coloured chest patch. Some females of a distinct race have Kestrel-like reddish brown colouring on their backs. Such females are more frequently seen further south. Juveniles can best be distinguished from mature females by a white patch on their napes. Cuckoos have yellow legs. Their beaks have a brown upper mandible and a greenish lower mandible with a pale base. Their irises may be yellowish orange (adults) or reddish brown (juveniles), and they have yellow eyelids.