How important are pelagic preys for the Kelp Gulls during the chick rearing at South Shetland Islands?

FAVERO M & MP SILVA.

POLAR BIOLOGY

Año: 1998 vol. 19 p. 32 - 36

0722-4060

An analysis of pellets regurgitated indicated adult kelp gulls (Larus dominicanus) on the South Shetland Islands consumed predominantly intertidal prey, whereas previous studies at Antarctic Peninsula sites have reported kelp gulls consuming predominantly pelagic species. The pellets collected at Nelson Island during the chick-rearing period indicated that the limpet Nacella concinna was their most frequent prey, followed by carrion, gammariids, snails and krill. Fish were scarcely represented. Also, regurgitated stomach contents of chicks showed that limpets and carrion were the most frequent food items, accounting for 70% of the mass. However, gammariids were particularly important by number. Signi®cant di€erences were observed in the overall comparison of the diet as re¯ected by the two sampling methods. In general, the importance of pelagic prey was negligible when compared to intertidal or scavenged prey. Our results di€er greatly from those reported for the Antarctic Peninsula, where chicks were almost exclusively fed with the pelagic ®sh Pleuragramma antarcticum. These di€erences could be related to the abundance of pelagic resources in southernmost latitudes, and/or to the presence of more extensive intertidal foraging areas at the South Shetland Islands.Larus dominicanus) on the South Shetland Islands consumed predominantly intertidal prey, whereas previous studies at Antarctic Peninsula sites have reported kelp gulls consuming predominantly pelagic species. The pellets collected at Nelson Island during the chick-rearing period indicated that the limpet Nacella concinna was their most frequent prey, followed by carrion, gammariids, snails and krill. Fish were scarcely represented. Also, regurgitated stomach contents of chicks showed that limpets and carrion were the most frequent food items, accounting for 70% of the mass. However, gammariids were particularly important by number. Signi®cant di€erences were observed in the overall comparison of the diet as re¯ected by the two sampling methods. In general, the importance of pelagic prey was negligible when compared to intertidal or scavenged prey. Our results di€er greatly from those reported for the Antarctic Peninsula, where chicks were almost exclusively fed with the pelagic ®sh Pleuragramma antarcticum. These di€erences could be related to the abundance of pelagic resources in southernmost latitudes, and/or to the presence of more extensive intertidal foraging areas at the South Shetland Islands.