Streaked Shearwater

Streaked Shearwater (Calonectris leucomelas) is a large shearwater with white underparts, grey-brown upperwings and a pale head marked by dark streaks across the crown 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 ranges over the north-western Pacific, feeding on fish and squid at sea and returning to islands to nest in burrows, where activity around colonies is mainly nocturnal. 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).