Tristan albatross  (Diomedea dabbenena)

With an enormous wingspan that can exceed three metres, the huge Tristan albatross is well adapted for gliding the ocean airs (2). Previously considered a member of the wandering albatross (Diomedea exulans) species, these birds share an extremely similar plumage (3). Adults are white, with a dark upperwing (4). The two species are probably indistinguishable in the field, but the Tristan albatross is generally smaller, darker and slower to acquire the white adult plumage (3).

Breeding populations are restricted to the Tristan da Cunha group of islands in the Southern Atlantic Ocean. Extinct on the main island of Tristan, the chief colony now exists on Gough Island, with two to three breeding pairs on Inaccessible Island. The annual breeding population on Gough Island varies from year to year, but is estimated to be between 1,500 and 2,400 pairs. Outside of the breeding season, the Tristan albatross disperses to South Atlantic and South African waters, with numerous recent records from Brazilian waters and one from Australia, showing that these birds travel into the Indian Ocean (3).

Nesting occurs above the tree line, between 400 and 700 meters, primarily on slopes in wet heath (3) (5) (6). Otherwise a pelagic species, found over the open ocean far from shore (5).

As with other albatross species, fidelity to partners and to the breeding colony is high (7). These albatross have a slow reproductive rate, producing just one egg every two years (3) (8). Egg-laying occurs from December to February, and the chick fledges the following November to February (8). Young birds return to the islands after three to four years (four to five years old) and usually first breed at eight years of age, but some breed as young as six (7).

This albatross feeds in the open ocean on fish, squid and crustaceans (5), and probably follows ships and trawlers for offal and galley refuse (2).

The Tristan Albatross is in grave danger of becoming extinct in the foreseeable future, with numbers having decreased by 28 percent over 46 years on Gough Island, disappeared almost entirely on Inaccessible Island and already become extinct on Tristan da Cunha. The dramatic decline in numbers on Inaccessible Island is attributed to predation by feral pigs (now absent) and humans, while the extinction on Tristan was probably the result of human exploitation, in addition to predation by rats. On Gough, storms have caused peat slips that have buried and killed nesting adults, although this is likely to be only a very rare occurrence (3). The main threat comes from bycatch from longline fisheries, with satellite tracking indicating a substantial overlap between the range of these birds and areas where longline fisheries are well known for their high rates of seabird bycatch mortality (3) (9). Further more, if one parent is lost at sea the other cannot cope with the food demands of their chick and the chick will most probably die. Astonishing recent research has also shown that invasive, introduced house mice, three times the size of those in Europe, are also devastating seabird populations on Gough Island by preying upon chicks (3) (10). The chicks are up to 250 times the weight of the mice but are largely immobile and defenceless, the species having evolved over millions of years on an island with no natural predators (10). Approximately 1,000 Tristan albatross chicks are thought to be killed each year by these seemingly unlikely predators (10).

The Tristan albatross is listed on Annex 1 of the Agreement on the Conservation of Albatrosses and Petrels (ACAP), which seeks to coordinate activity to mitigate known threats to albatrosses. Gough and Inaccessible Island are nature reserves, and together form a World Heritage Site. Both islands are uninhabited, apart from a meteorological station on Gough. Satellite tracking monitors the dispersal of these birds, which helps provide information on the potential impact of longline fisheries. Educating fisheries about mitigation measures to reduce bycatch mortality is an ongoing conservation priority for all albatross species (3). The Royal Society for the Protection of Birds (RSPB) has been awarded £60,000 by the UK government's Overseas Territories Environment Programme to fund additional research into chick predation by mice and how to deal with it (10). Such investment is vital, but without addressing both adult and chick mortality, this magnificent albatross will continue to decline (6).

For further information on the Tristan albatross see:

BirdLife International:
http://www.birdlife.org/datazone/species/

Save the Albatross:
http://www.savethealbatross.net/

Authenticated (15/05/07) by Ross Wanless and Andrea Angel, Percy Fitzpatrick Institute of African Ornithology. 
http://www.fitzpatrick.uct.ac.za