Guide to North American Birds

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Adult. Photo: Tom Benson/Flickr (CC BY NC ND 2.0)

South Polar Skua

Stercorarius maccormicki

It occurs regularly off both our coasts, but this predatory seabird nests only far to the south of us, around the edges of the Antarctic continent. When it reaches North American waters it remains far offshore, pirating food from other seabirds or catching its own fish.

Conservation status	Numbers apparently stable. Except near a few Antarctic research stations, the haunts of the species are usually remote from the impacts of human activities.
Family	Skuas and Jaegers
Habitat	Open ocean. Ranges widely at sea, over both warm and very cold waters. Appears far off North American coast where there are concentrations of other birds from which to steal food. Almost never seen from shore on this continent. Nests in Antarctica, on islands and mainland, on barren ground.

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Feeding Behavior

Forages at sea by plunging into water from flight, or by seizing items while sitting on surface. Often steals food from other seabirds: may grab a shearwater or gull with its bill and shake the other bird violently to make it disgorge its catch.

Eggs

Two, sometimes one. Olive to brown, blotched with darker brown. Incubation is by both sexes, but female does more. Incubation period 24-34 days, usually 28-29. Young: Both parents feed young, by regurgitation. Young may leave nest soon after hatching, wander in immediate vicinity. Although both eggs usually hatch, usually only one young survives to fledging. Age at first flight 49-59 days.

Young

Both parents feed young, by regurgitation. Young may leave nest soon after hatching, wander in immediate vicinity. Although both eggs usually hatch, usually only one young survives to fledging. Age at first flight 49-59 days.

Diet

Mainly fish. Diet in North American waters not well known, but feeds mostly on fish while at sea. On breeding grounds, some feed mainly on the eggs and young of penguins, and on carrion around penguin colonies.

Nesting

In Antarctic, some nest close to penguin colonies, feeding on eggs and chicks. Where this species overlaps with the larger Brown Skua, the Browns effectively "control" the penguin colonies, and the South Polars must forage at sea. Courtship involves much posturing and calling; male feeds female. Usually first breeds at age of 5-6 years; birds usually have same mates and same nest sites every year thereafter. In aggressive display near nest, both wings are raised together over back, head extended forward while bird gives harsh calls. Nest site is on ground. Nest is simple scrape in soil or moss; often begun by male and completed by female.

Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds

Migration

From Antarctic nesting grounds, moves far to the north in both Atlantic and Pacific. Perhaps most common off southern California in late spring, off northern California in early fall, and off New England in early summer, but details still poorly known.