Albatrosses, of the biological family Diomedeidae, are large seabirds related to the procellariids, storm petrels, and diving petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North Pacific. They are absent from the North Atlantic, although fossil remains show they once occurred there and occasional vagrants are found. Albatrosses are among the largest of flying birds, and species of the genus Diomedea (great albatrosses) have the longest wingspans of any extant birds, reaching up to 3.7 m (12 ft). The albatrosses are usually regarded as falling into four genera, but disagreement exists over the number of species.
Albatrosses are highly efficient in the air, using dynamic soaring and slope soaring to cover great distances with little exertion. They feed on squid, fish, and krill by either scavenging, surface seizing, or diving. Albatrosses are colonial, nesting for the most part on remote oceanic islands, often with several species nesting together. Pair bonds between males and females form over several years, with the use of "ritualised dances", and last for the life of the pair. A breeding season can take over a year from laying to fledging, with a single egg laid in each breeding attempt. A Laysan albatross, named Wisdom, on Midway Island is the oldest-known wild bird in the world; she was first banded in 1956 by Chandler Robbins.
Of the 22 species of albatrosses recognised by the IUCN, 21 are listed as at some level of concern; two species are critically endangered, seven species are endangered, six species are near threatened, and six species are vulnerable. Numbers of albatrosses have declined in the past due to harvesting for feathers. Albatrosses are threatened by introduced species, such as rats and feral cats that attack eggs, chicks, and nesting adults; by pollution; by a serious decline in fish stocks in many regions largely due to overfishing; and by longline fishing. Longline fisheries pose the greatest threat, as feeding birds are attracted to the bait, become hooked on the lines, and drown. Identified stakeholders such as governments, conservation organisations, and people in the fishing industry are all working toward reducing this bycatch.
Most albatrosses range in the Southern Hemisphere from Antarctica to Australia, South Africa, and South America. The exceptions to this are the four North Pacific albatrosses, of which three occur exclusively in the North Pacific, from Hawaii to Japan, California, and Alaska; and one, the waved albatross, breeds in the Galápagos Islands and feeds off the coast of South America. The need for wind to enable gliding is the reason albatrosses are for the most part confined to higher latitudes; being unsuited to sustained flapping flight makes crossing the doldrums extremely difficult. The exception, the waved albatross, is able to live in the equatorial waters around the Galápagos Islands because of the cool waters of the Humboldt Current and the resulting winds.
Why the albatrosses became extinct in the North Atlantic is unknown for certain, although rising sea levels due to an interglacial warming period are thought to have submerged the site of a short-tailed albatross colony that has been excavated in Bermuda. Some southern species have occasionally turned up as vagrants in the North Atlantic and can become exiled, remaining there for decades. One of these exiles, a black-browed albatross, returned to gannet colonies in Scotland for many years in an attempt to breed.
The use of satellite tracking is teaching scientists a great deal about the way albatrosses range across the ocean to find food. They undertake no annual migration, but disperse widely after breeding; Southern Hemisphere species often undertake circumpolar trips. Evidence also exists of separate ranges for different species at sea. A comparison of the foraging niches of two related species that breed on Campbell Island, the Campbell albatross and the grey-headed albatross, showed the Campbell albatross primarily fed over the Campbell Plateau, whereas the grey-headed albatross fed in more pelagic, oceanic waters. Wandering albatrosses also react strongly to bathymetry, feeding only in waters deeper than 1000 m (3281 ft); so rigidly did the satellite plots match this contour that one scientist remarked, "It almost appears as if the birds notice and obey a 'No Entry' sign where the water shallows to less than 1000 m". Also, evidence shows different ranges for the two sexes of the same species; a study of Tristan albatrosses breeding on Gough Island showed that males foraged to the west of Gough and females to the east.