Least Auklet

Least Auklet (Aethia pusilla) is the smallest North Pacific auk, dark above and white below with a short bill and tiny facial plumes. 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 gathers in immense colonies and dives for copepods and other zooplankton over productive shelf waters. 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).