Thalassarche chrysostoma has a circumpolar distribution over cold subantarctic and Antarctic waters34. It breeds on South Georgia (Georgias del Sur), Islas Diego Ramirez and Ildefonso (Chile), Prince Edward and Marion Islands (South Africa), Crozet Islands, Kerguelen Islands (French Southern Territories), Campbell Island (New Zealand) and Macquarie Island (Australia). The annual breeding population is c.99,000 pairs, equivalent to a total population of c.250,000 mature individuals in this biennially breeding bird20, 29. Approximately half the global population occurs on South Georgia34. Its range at sea while breeding lies largely within or south of the Antarctic Polar Frontal Zone12,15. At South Georgia the population has declined by at least 20.9% between 1985 and 2004, and at a possibly even greater rate due to declines of 2.2% in mixed colonies with T. melanophrys. The trend for Bird Island, South Georgia shows an even greater decline of 2.9% decrease per annum between 1991 and 200434. At Marion Island the population increased by 2.5% per annum between 1975 and 2007, increasing at a slower rate of 0.6% from 1988. However, 16 years of continous data now shows that the population decreased at a rate of 0.6% per year between 1991 and 200734. At Campbell, the population has declined by 79-87% since the 1940s13. Trends are unknown for the Chilean islands. The small population at Macquarie Island was stable between 1995 and 2007, and is likely to have been so since the mid-1970s34. Documented declines to date suggest the population has decreased by 15% since the mid-1980s; if current trends continue into the future, declines can be expected to equate to 66% over three generations (90 years). However, given the uncertainty around these estimates, particularly in the future, and the long trend period, a decline of 30-49% over 90 years is provisionally estimated. During the non-breeding season South Georgia birds have been recorded making one or more global circumnavigations, the fastest in just 46 days22. All New Zealand banded birds have been recovered west of New Zealand in Australian zone28.
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