ナンキョクアジサシ Sterna vittata

A light gray medium-sized tern. Black cap extends to bill in breeding plumage. Bill and legs red. In non-breeding birds, cap reduced to just the area behind the eye, bill has dull pinkish color, and underparts are white. Breeds in the circumpolar subantarctic region. Generally known to stay close to their breeding sites. Migrating Arctic Tern could occur in the same area, but not in breeding plumage, and would show more prominent black markings on outer primaries. White-fronted Tern can be distinguished by its larger body, lighter coloring, and longer, thinner, all-black bill.