Juan Fernandez Petrel

Juan Fernandez Petrel (Pterodroma externa) is a grey-and-white gadfly petrel with long pointed wings, a dark cap and a dark M-shaped pattern across the 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 a single island in Chile's Juan Fernández Archipelago and ranges widely over Pacific waters, taking squid, fish and crustaceans from near the 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).