The species diversity in Antarctica is very low, and nearly all of the 43 species of birds which normally occur south of the Antarctic Convergence are sea birds. Of the approximately 8,600 species of living bird species known today, only 287 are classified as sea birds (about 3%). However, keeping in mind that about 70% of the world is covered by oceans, it is not surprising that the bird species with the largest populations are sea birds. Some ornithologists believe the Wilson's storm petrel, which breeds by the millions in Antarctica, may be the commonest bird in the world.
Antarctica and its associated islands provide excellent breeding grounds for countless sea birds, which include seven species of penguins, four albatrosses, 15 petrels and shearwaters, three storm petrels, two diving petrels, one cormorant, one gull, three terns, two skuas, and two sheathbills (as well as a few non-sea birds…two ducks and one pipit).
As we sail for Antarctica, we always encounter albatrosses…those majestic, amazing members of a group of birds known as the tube-nosed swimmers. Many ornithologists believe the extended tube enables these birds to eject the concentrated brine produced by the salt gland away from the face, so it will not dry and crystallize on the facial feathers. Thick salt deposits on the face could be a serious problem to birds that inhabit such cold and windy environments as Antarctica, because they do not normally get many chances to clean and preen themselves. This group also includes shearwaters and petrels, storm-petrels, and diving petrels.
The albatrosses are easily identified by their large size, long narrow wings, short tails, and distinctive flight patterns. They spend most of their lives in the air and have perfected a gliding flight which allows them to stay airborne with a minimum of effort. It’s as though they actually seem to enjoy windy, stormy conditions. It is great fun to watch as they swoop downwards with the wind just over the waves, then turn into the wind to gain height, and then reverse themselves to pick up speed and glide with the wind again. They seem to go on for hours like this without ever having to flap their wings. We usually encounter albatrosses in the open sea, and they often follow our ship taking advantage of the currents of air produced as the vessel moves, hoping for something edible to be dumped overboard or stirred up to the surface by the propellers. They feed mostly on squids, small fishes, and krill, which they catch by alighting on the surface and dipping their heads underwater. These birds have short, strong legs and webbed feet, and will alight readily on the water to rest or swim around after food. They usually must run along the surface into the wind in order to become airborne again.
For identification purposes, albatrosses can be categorized as large or small. The two large species (royal and wandering albatrosses) have the longest wings of any living birds, reaching a total wingspan of more than 3 m (10 ft). The small albatrosses are often called mollymawks, and usually have wingspans of about 2 m (6.5 ft). Most albatrosses have developed complex nuptial dances, and they begin to breed in late spring or early Summer. They nest on islands that provide good sites for taking off into the prevailing winds. Their nests often consist of mounds built out of mud, grasses, moss, etc., and excrement. Albatrosses lay just one egg. Incubation normally varies from 60 to 70 days in the small species, and lasts about 80 days in the large species. Both sexes incubate the egg, and feed the chick at the nest with regurgitated food until it fledges. The small albatrosses breed every year, but the two large species only breed every other year.
South Georgia is the most important breeding site for wandering albatrosses and there are about 4,000 annually breeding pairs. These incredible birds have the largest wingspan of any living species (upwards to 12 feet or 3.6 meters). They lay a single egg in mid-summer, which hatches after about 2.5 months. The hatchling then stays in the nest throughout the winter and fledges the following November or December. Wandering albatrosses fly incredible distances between the nesting sites here in South Georgia and the feeding grounds off eastern South America, so it takes a lot of effort to raise the single chick. It’s no wonder they only breed every other year. Sadly, their population is declining because of the scourge of illegal long-line fishing boats...the birds become hooked as the baited lines are set out and they are subsequently drowned, but fishing methods have been developed that eliminate this threat and it is hoped all the southern long-line fishing fleets will adopt them.