The resource of Antarctic and subantarctic waters supports vast numbers of a variety of seabirds, which play an important role in the marine ecosystem. While penguins and albatrosses are perhaps the best known of Antarctic marine birds, petrels, prions, fulmars and shearwaters form the majority of species that inhabit the region. Nesting grounds are limited, being confined to the scattered subantarctic islands and ice-free localities during the austral summer on the Antarctic continent and Antarctic Peninsula.
Many of the birds of the Antarctic and sub-Antarctic are susceptible to environmental change. They tend to have low reproduction rates and thereby low potential for population recovery. Impacts from human disturbance, such as long-line fisheries, are a further threat to the populations of certain albatross and petrel species.
Only a few species of Antarctic seabird are adapted to breed regularly on the Antarctic continent. Petrels, like albatrosses, feed mostly on fish, squid and crustaceans from the ocean. Some species will also feed on eggs and chicks of other birds, placentas and dead pups from seal pupping grounds, and various other carrion. Petrels and other members of the Procellariidae family (albatrosses, prions, fulmars and shearwaters) lay a single egg, are generally colonial, and both parents share incubation and chick-rearing duties.
Along with emperor and Adélie penguins, Antarctic snow petrels (Pagodroma nivea) are the most abundant species. The birds’ behavioural adaptions and physiological characteristics such as subdermal fat and layers of down and feathers are crucial to their ability to survive in such climatic extremes. Snow petrels are pure white with black under down and conspicuous black eyes. They have a small black bill and bluish gray feet. They are restricted almost exclusively to cold Antarctic waters, preferring pack ice, icebergs and ice floes as their main habitat.
Snow petrels tend to fly low over the water but very high over land to avoid predators such as South Polar skuas. Their flight is more fluttering than most petrels. They feed mainly by surface-dipping while on the wing. Unlike most of the petrel family, Snow petrels are nervous at the nest and will desert their eggs if overly disturbed.
Antarctic petrels prefer to live near the pack-ice, icebergs, ice floes but nest inland on the Antarctic continent.
Old-time whalers used to call Giant petrels ‘breakbones’ because of their frequent blood-stained brawls over carrion meat.
Diving petrels are small seabirds with stubby wings that seem to whir like wind-up toys as they buzz about the sky in perpetual motion. Where most petrels flap and glide, diving petrels actually ‘fly’ under water quite similar to penguins.
Storm petrels are the smallest and lightest seabirds in the world. The Wilson’s storm petrel skips across the surface of the water as it feeds, stirring up small marine organisms with its feet. Wilson’s storm petrels feed while on the wing, skimming and pattering with their feet over the sea surface.
White-chinned petrels have been called ‘cape hens’ and also ‘shoemakers,’ the latter based on their call, which resembles that of a cobbler hammering shoes.
South Polar skuas (Catharacta maccormicki) are widespread and prominent in the Antarctic. These birds are notorious for their scavenging behaviour, particularly their acts of piracy in pursuing other seabirds and forcing them to drop their catch. This is called ‘kleptoparasitism.’ They also prey heavily on the eggs and chicks of penguins and small petrels.
The South Polar skua is recognised as the world’s most southerly bird. Sightings have occurred even at the south pole. 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.
The Brown Skua (Catharacta antarctica) is found on Signy Island, one of the remote South Orkney Islands, which lie more than 1300 km from the Falkland Islands, 900 km from South Georgia and 600 km from the Antarctic Peninsula.
Marine birds of the Southern ocean also include gulls, terns and two species of cormorant. Endemic terrestrial birds of this region are few and include the South Georgia pipit (Anthus antarcticus) and species of freshwater duck on South Georgia and Kerguelen.
Two species of sheathbill, pigeon-like shorebirds of scavenging habit, are also restricted to the region. Many other landbirds have been recorded as vagrants, but these invariably succumb to the extreme conditions or predators.