Stejneger's Petrel

Stejneger's Petrel (Pterodroma longirostris) is a small grey-and-white gadfly petrel with a dark cap and an M-shaped pattern across its long upperwings. 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 islands of the Juan Fernández group, disperses widely across the Pacific and takes squid, fish and crustaceans from the ocean surface. 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).