Arctic Tern

Arctic Tern (Sterna paradisaea) is a slim tern with very long tail streamers, short red legs, red bill and a black cap. 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 comparisons with similar species in the same habitat (Wikipedia, general species account).

It plunge-dives for fish and makes immense migrations between Arctic breeding grounds and Antarctic waters. 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).