South Polar Skua
Encyclopedia
The South Polar Skua, Stercorarius maccormicki, is a large seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...

 in the skua
Skua
The skuas are a group of seabirds with about seven species forming the family Stercorariidae and the genus Stercorarius. The three smaller skuas are called jaegers in North America....

 family Stercorariidae. An older name for the bird is MacCormick’s Skua, after explorer and naval surgeon Robert McCormick
Robert McCormick (explorer)
Robert McCormick was a British Royal Navy surgeon, explorer and naturalist.McCormick was born in Great Yarmouth, England...

, who first collected the type specimen. This species and the other large southern hemisphere skuas, together with Great Skua
Great Skua
The Great Skua, Stercorarius skua, is a large seabird in the skua family Stercorariidae. In Britain, it is sometimes known by the name Bonxie, a Shetland name of unknown origin.-Description:...

, are sometimes placed in a separate genus Catharacta.

The South Polar Skua is a large bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

 (though small compared to other skuas sometimes placed in Catharacta) that measures approximately 53 centimetres (20.9 in) in length. It breeds on Antarctic
Antarctic
The Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...

 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
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...

, wintering at sea in the Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, Indian
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 and Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

s. 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 gull
Gull
Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...

s, tern
Tern
Terns are seabirds in the family Sternidae, previously considered a subfamily of the gull family Laridae . They form a lineage with the gulls and skimmers which in turn is related to skuas and auks...

s and even gannet
Gannet
Gannets are seabirds comprising the genus Morus, in the family Sulidae, closely related to the boobies.The gannets are large black and white birds with yellow heads. They have long pointed wings and long bills. Northern gannets are the largest seabirds in the North Atlantic, with a wingspan of up...

s of their catches. It will also directly attack and kill other seabirds and their chicks. It also eats scraps and carrion
Carrion
Carrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...

. These birds are also capable of swallowing large items, such as a whole dim sim.

Like most other skua species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, it continues this piratical behaviour throughout the year, showing less agility and more brute force than the smaller skuas (jaegers) when it harasses its victims.

Distinguishing this skua from the northern hemisphere Arctic
Arctic Skua
The Parasitic Jaeger, also known as the Arctic Skua or Parasitic Skua, is a seabird in the skua family Stercorariidae....

, Pomarine
Pomarine Skua
The Pomarine Skua, Stercorarius pomarinus, known as Pomarine Jaeger in North America, is a seabird in the skua family Stercorariidae. It is a migrant, wintering at sea in the tropical oceans.- Taxonomy :...

  and Long-tailed Skua
Long-tailed Skua
The Long-tailed Skua, Stercorarius longicaudus is a seabird in the skua family Stercorariidae....

s 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
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

. Similar problems occur, of course, with extra-limital claims of Great Skua.

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