From this point of view, this picture could have easily been taken in the Arctic. In that case, this would be an Arctic Tern, but in this case the picture is from  Antarctica, which makes it an Antarctic Tern. There are also Arctic Terns in Antarctica (in the northern winter they come all the way to Antarctica), but they do have their winter plumage, which looks quite different from this.

In this case the tern has just caught a small crustacean, probably to bring to their small chick.