Western Sandpiper

Western Sandpiper (Calidris mauri) is a tiny shorebird with black legs, slightly drooping bill and rufous crown and scapulars in breeding plumage. 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 in western Alaska and migrates in huge flocks to tidal flats, feeding on small invertebrates and biofilm. 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).