Does prey availability influence the foraging effort and breeding success in the Antarctic Shag Phalacrocorax bransfieldensis?

CASAUX R,

Chinese Birds

China Ornithological Society

Año: 2013 vol. 4 p. 240 - 247

1674-7674

Abstract Information on diet composition, foraging effort and breeding success of the AntarcticShag (Phalacrocorax bransfieldensis) was obtained at three colonies on the Antarctic Peninsula, duringthe 1997/98 breeding season. Fish was the most important prey at each of the colonies sampled,followed by octopods and gastropods. Among colonies, there were marked differences in the size ofthe fish consumed, which was smaller at Py Point. This was mainly due to the larger number of specimensof the smallest fish prey species consumed there. Shags from Py Point performed longer foragingtrips and spent more time per day foraging. Although at the beginning of the study the numberof chicks per nest observed at the three colonies was similar, the number surviving to fledge at PyPoint was markedly lower. The relative higher foraging effort and lower breeding success observed atPy Point might be related to the differences in the fish consumed between colonies. My results suggestthat the decline in the inshore fish populations observed around the South Shetland Islands could beone of the reasons explaining the steady decrease in the number of breeding Antarctic Shags observedat colonies monitored in this archipelago.