Masked Booby

Masked Booby (Sula dactylatra) is the largest booby, with a mostly white body, black flight feathers and tail, and a dark mask around the bill. 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 forages over tropical oceans by powerful plunge-dives for fish and squid, and breeds in open ground colonies on remote islands. 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).