
Photo: Andrew Bazdyrev · CC BY 4.0
Cuculus poliocephalus
Rare visitor: recorded only occasionally in this country
Lesser Cuckoo (Cuculus poliocephalus) is a small grey cuckoo with barred underparts, pointed wings and a long tail, resembling a compact Common Cuckoo. The combination of body shape, bill structure, plumage pattern and voice provides the most useful field characters. Age, sex and season can alter its appearance, so identification should use several features rather than colour alone. This supports comparison with similar species in the field (Wikipedia, general species account).
It breeds across parts of Asia, eats mainly insects and lays its eggs in nests of smaller host birds. Its movements and social behaviour vary through the year, with breeding birds generally more dispersed and non-breeding birds more likely to gather where food is concentrated. Japanese records place it within the country's documented avifauna as a resident, migrant, visitor or introduced bird (Wikipedia, general species account; Wildlife of Japan occurrence records).