Common Cuckoo

The Common Cuckoo is a slender, long-tailed bird whose barred underparts and grey upperparts can create a hawk-like impression. This resemblance to a sparrowhawk may reduce attacks by small birds or help a female approach a host nest. The familiar male call gave the bird its English name, while females use different vocalisations. Several subspecies occur across Eurasia, including forms breeding through northern Asia and Mongolia, and plumage also includes a less frequent reddish-brown female morph. (Wikipedia, general species account)

This cuckoo is a brood parasite: the female places an egg in another bird's nest, and the young cuckoo is raised by the host. Different female lines specialise on particular hosts, producing eggs that resemble those of species such as reed warblers, meadow pipits or dunnocks. Adults feed chiefly on insects and are notably willing to eat hairy caterpillars avoided by many birds. The species is strongly migratory, breeding across Europe and Asia before travelling to Africa or southern Asia for winter. (Wikipedia, general species account)