Antarctic Tern (Sterna vittata)
The Antarctic Tern (Sterna vittata) is a typical tern. It ranges throughout the southern oceans. It is very similar in appearance to the closely related Arctic tern, but is stockier, and the wing tips are grey instead of blackish in flight. It is, of course, in breeding plumage in the southern summer, when the Arctic tern has moulted to its non-breeding plumage (though this is not useful for separating it from another species, the South American tern).
Breeding takes place from mid-November to early December. Chicks hatch from December to February. Skuas and jaegers are the primary predators of this bird's eggs and young.
The total global population of this bird is around 140,000 individuals. (wikipedia)
Seen in decent numbers around South Georgia but fewer birds around the Antarctic peninsula and South Shetland Islands. This is an adult at the wharf in Grytvikan.