Foraging movements of the Southern Giant Petrel at the Patagonian shelf: a comparative study between colonies of Argentina

QUINTANA, F.; DELL’ARCIPRETE, P.

Montevideo, Uruguay

Congreso; Third International Albatross and Petrel Conference, IAPC; 2004

We study at-sea movements and foraging ranges of the Southern Giant Petrel, Macronectes giganteus, from the only two breeding sites along the Patagonian coast of Argentina. During late incubation and chick-rearing periods we satellite-tracked 9 breeders from the northern nesting site (NS) (I. Arce and G. Robredo colonies, 45o04’S, 65o45’W) and 7 breeders from the southern nesting site (SS) (Isla de los Estados, 54o 40’S, 64o 08’W). NS females typically foraged East/Southeast from the colony, over the middle continental shelf (100 m deep) and the shelf break, between 43º and 51º S. SS females fed around Isla de los Estados at the shelf break between 51o and 56o S. Foraging areas of birds from the two sites did not overlapped. The foraging range of NS females was, on average, 50% larger than that of SS females. The maximum distance covered by SS females during foraging trips was considerably shorter than NS females (means: 214 vs. 423 km), probably as a consequence of the proximity of the shelf break. Males from both nesting sites stayed associated to coastal areas and showed a clear spatial association with areas of high concentration of penguins and sea lions. In contrast to other breeding populations of Southern Giant Petrels, the numbers of breeding pairs of the two studied sites are apparently increasing.