Short CommunicationRecent distributional changes of seabirds in South Africa: is climate having an impact?

Abstract

There have been recent changes in the distributions of several seabirds in South Africa. In the mid-1990s, breeding of Leach's storm petrel Oceanodroma leucorhoa was recorded in the Western Cape, the first record for the Southern Hemisphere. There was a large eastward expansion in the breeding range of crowned cormorant Phalacrocorax coronatus sometime between the early 1990s and the early 2000s, and in that of Hartlaub's gull Larus hartlaubii between 1995 and 2000. A smaller eastward expansion in the breeding range of kelp gull Larus dominicanus was noted in 2006. In 2003, a new colony of African penguins Spheniscus demersus formed in the east of the Western Cape, but after 2004 there were large decreases of penguins at colonies in the west of this province. South Africa's northern most penguin colony became extinct in 2006. In the early 2000s, there was a decrease in numbers of Cape gannets Morus capensis breeding in the Western Cape, but a large increase in the Eastern Cape. Numbers of Cape P. capensis and bank P. neglectus cormorants decreased in the north of the Western Cape in the 1990s, but increased at some southern localities in the 2000s. A similar pattern was noted for kelp gulls, except that the decreases in the north took place in the 2000s. The proportion of swift terns Sterna bergii in the Western Cape that bred in the south of this province increased markedly in the mid-2000s. Although local factors may have played a role in the distributional changes, their consistent anticlockwise nature, the broad similarity in their timing and their widespread occurrence suggest the influence of environmental change, perhaps forced by climate. This hypothesis is supported by similar displacements of other South African marine resources and congruent changes in seabird populations in the South-West Indian Ocean.

Keywords: climate change; colonisation; distributional shift; range expansion; seabird; South Africa

African Journal of Marine Science 2008, 30(1): 189–193