Breeding seabirds at Dassen Island, South Africa: Chances of surviving great white pelican predation

Abstract

Seabird predation by great white pelicans Pelecanus onocrotalus is an unusual phenomenon that has become increasingly frequent in the Western Cape, South Africa. We report the scale of pelican predation and its impact on the breeding success of 5 seabird species monitored at Dassen Island in 2006. Pelican predation was observed on chicks of kelp gulls Larus dominicanus, crowned cormorants Phalacrocorax coronatus and Cape cormorants Phalacrocorax capensis. No predation on eggs was seen. Breeding success for 4 of the 5 species studied was low, with the white-breasted cormorants Phalacrocorax lucidus having the highest breeding success (0.56 fledglings per nest). Cape and bank cormorants Phalacrocorax neglectus did not fledge any chicks, while crowned cormorants had a breeding success of 0.08 fledglings per nest. Kelp gulls had a hatching success of 46%, but only a few chicks fledged, giving a breeding success of 0.06 fledglings per nest. Pelican predation poses a threat to at least 3 of the 5 seabirds studied, all of which are endemic to southern Africa. Three species are globally Endangered or Near Threatened, and pelican predation places additional pressure on these species. Management actions are needed to reduce or eliminate pelican predation. © Inter-Research 2010.