Black-legged Kittiwake

Black-legged Kittiwake (Rissa tridactyla) is a small oceanic gull with a yellow bill, black legs and neat black triangular wingtips lacking white spots. Body shape, bill structure, plumage pattern and voice provide the strongest field characters. Age, sex and season may alter its appearance, so identification should combine several features and careful direct field comparisons with similar species in the same habitat (Wikipedia, general species account).

It feeds mainly on small fish and marine invertebrates and nests in dense colonies on narrow sea-cliff ledges. Its movements and social behaviour vary through the year, with breeding birds generally more dispersed and non-breeding birds gathering where food is concentrated. Japanese records place it within the country's documented avifauna as a resident, migrant or visitor (Wikipedia, general species account; Wildlife of Japan occurrence records).