The South Polar Skua, Stercorarius maccormicki, is a large seabird in the skua family Stercorariidae. An older name for this bird is MacCormick's Skua. This species and the other large southern hemisphere skuas, together with Great Skua, are sometimes placed in a separate genus Catharacta.

This is a large bird at 53 cm length. It breeds on Antarctic coasts, usually laying two eggs in November and December. Like other skuas, it will fly at the head of a human or other intruder approaching its nest. It is a migrant, wintering at sea in the Pacific Indian and Atlantic Oceans. In the eastern North Atlantic it is replaced by the Great Skua.

The South Polar Skua eats mainly fish, which it often obtains by robbing gulls, terns and even gannets of their catches. It will also directly attack and kill other seabirds.

Like most other skua species, it continues this piratical behaviour throughout the year, showing less agility and more brute force than the smaller skuas when it harasses its victims.

Distinguishing this skua from the northern hemisphere Arctic, Pomarine and Long-tailed Skuas is relatively straightforward. The large size, massive barrel chest and white wing flashes of this bird are distinctive even at a distance. The flight is direct and powerful.

Identification of this skua is more complicated when it is necessary to distinguish it from the closely-related Great Skua of the North Atlantic, and the other large southern hemisphere skuas.

Adult South Polar Skuas are greyish brown above, and have a whitish (pale morph) or straw-brown (intermediate morph) head and underparts, and the contrast between head and body makes it easy to separate from similar species with good views.

Juveniles and adult dark morphs are harder to distinguish from their relatives, and more subjective or difficult-to-observe criteria, such as the colder brown plumage and blue bill base, must be used.

Identification problems make claims of any southern hemisphere skua in the eastern North Atlantic problematic, and few records of South Polar Skua have been accepted in Western Europe. Similar problems occur, of course, with extra-limital claims of Great Skua.

This bird is named after the naval surgeon Robert McCormick, who collected the type specimen.

A Skua at Rothera

South Polar Skua, Hannah Point, Livingston Island: 62°39'S, 60°36'W, Antarctic Peninsula.

In popular culture

• In the film Happy Feet, young Emperor Penguin Mumble is beset by 4 South Polar Skuas that have mobster accents, the leader of which, bores everyone with his 'alien abduction'.