Black-naped Tern

Black-naped Tern (Sterna sumatrana) is a slender tropical tern with white plumage, pale grey wings and a narrow black stripe through the eye and nape. 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 by plunge-diving for small fish around reefs and lagoons and nests on bare coral or rocky islands. 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).