Chinese Crested Tern

The Chinese crested tern is a 38–43 cm marine tern with a black crown in breeding plumage, pale silvery-grey back and wings, white tail and rump, and a stout yellow bill tipped black with a tiny white point. It resembles Sandwich and lesser crested terns, but the reversed yellow-and-black bill pattern, pale mantle and white rump are useful distinctions. Greater crested tern is larger, darker and has an entirely yellow bill (Wikipedia, general species account).

Thalasseus bernsteini is closely related to the greater crested tern and has hybridized with it. The species was once called Sterna zimmermanni until rediscovery of Hermann Schlegel's older type specimen in 1975 established the current name. After being feared extinct, four pairs were found in 2000 nesting within a greater crested tern colony on an islet in the Matsu group. Korean sightings demand careful documentation because confusion with common crested terns is possible (Wikipedia, general species account).