Parasitic Jaeger

Parasitic Jaeger (Stercorarius parasiticus) is a fast, falcon-like seabird occurring in dark and pale morphs, with pointed central tail feathers as an adult. 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 breeds on tundra and moorland and frequently steals fish by pursuing gulls and terns during migration. 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).