South Polar Skua

Photograph Courtesy: National Science Foundation

 

Description & Characteristics:

Large, heavily built birds, skuas are closely related to members of the gull family. In North America the coastal skuas are known as jaegers. Two species of skuas are found in the southern oceans: the Antarctic or the Brown, and the South Polar. Antarctic skuas breed on most of the southern islands and may be distributed as far north as the subtropics, while South Polar skuas occur primarily on the Antarctic continent, although sightings have been recorded as far north as Greenland and the Aleutian Islands. South Polar skuas are often seen following ships at sea. In winter after the breeding season, both skua species migrate northward spending most of their time at sea.

In appearance, skuas look like immature gulls, although heavier, more robust and menacing in mien. They have conspicuous white patches at the base of their flying feathers, wedge-shaped tails, and a black, short heavy bill. Their flight is heavy, with relatively little gliding and much flapping.

All skuas are fiercely predatory, and the species of the Southern Ocean, are no exception. During the summer South Polar skuas stake territories near Adélie penguin rookeries on the coast, raiding them for eggs, chicks, and also cleaning up carrion. Thus, they have earned the nickname, 'raptor of the south'. The diet of Antarctic skuas is more broad depending on season and their locality. They may scavenge and predate upon other seabirds and their young and eggs, or they may roam the southern oceans feeding on fish, molluscs, squid, and crustaceans (mainly krill & copepods).

South Polar skuas arrive at their breeding colonies in late October to mid-December. They nest in sheltered areas adjacent to penguin colonies. The nests are shallow depressions on the ground and are often found on rocky outcrops, moss covered cliffsides or valley floors. South Polars will generally lay two mottled eggs which hatch in late December to late January after an incubation period of 24 to 34 days.

Antarctic skuas also breed during the summer months, typically laying two eggs in nests located on elevated grasslands or in sheltered rocky areas in close association with prey species. They will defend their territories vigorously against all intruders including other skuas and petrels. Some birds choose not to nest in the colonies, but will establish solitary nesting sites. Breeding skuas are highly territorial and will attack unwelcome intruders to their nests by flying straight for the head with claws outstretched.

The estimated lifespans of both South Polar and Antarctic skuas are approximately 11 years.


  Did you know?


- The South Polar skua is recognized as the world's most southerly bird: sightings have occurred even at the South Pole.

- At sea, South Polars may chase smaller seabirds to force them to regurgitate or drop their prey; this is called 'kleptoparasitism.'

- Some scientists believe decreases in skua populations on some islands may be due to declines in burrowing petrel numbers (a key prey species) from predation by introduced cats.

- Skuas like to bathe in freshwater pools.