Combining geographic information systems and stable isotope analysis to infer Magellanic Penguin diet in their austral distributio

JAVIER CIANCIO; ESTEBAN FRERE

Victoria

Congreso; 1st World Seabird Conference; 2010

Magellanic penguin (Spheniscus magellanicus) is the most outstanding seabird in the Atlantic Patagonia. Around a million pairs breed along the coast, having a predominant role as top predator. Penguins breeding in Santa Cruz and Tierra del Fuego consume almost 30000 tons of fish and squid during the breeding season. Previous trophic studies in the region were based in direct stomach analysis, while these studies offer accurate data on diet, they are restricted in time, showing the diet of the available prey during the sampling period. Recently, stable isotope analysis provided a reliable and integrative tool for trophic studies. We created a geographic information system including the distribution patterns of prey and penguins collected from published articles. We selected prey from the spatio-temporal overlap analysis and from published data and included in a stable isotopes mixing model to estimated proportions of prey consumed. Four main prey species and pectoral muscle of dead chicks from five colonies (Latitude 47-52 S) were collected. We assumed that the SI signature of chicks represented de diet during the last months in the vicinity of the colony. SIA analysis showed similar patterns to previous published data in accordance to spatio-temporal overlap analysis, with a diet based mainly on sprats in the southern colonies and more diverse in the North. This analysis also revealed a higher proportion of squids, a prey item generally underestimated by direct methods.