Habitat use and characterization of the seascape exploited by wintering adult and juvenile Southern Giant Petrels from Patagonia

GABRIELA S. BLANCO; JUAN P. PISONI; AGUSTINA GÓMEZ LAICH; FLAVIO QUINTANA

Cape Town

Congreso; 2nd World Seabird Conference; 2015

The characterization of the seascape used by top predators helps to understand the functioning ofmarine systems. The main goals of this study were to 1) analyze habitat use and at-sea movementsof adult and first year juvenile southern giant petrels (SGP, Macronectes giganteus) during theaustral winter, and 2) to characterize the oceanographic and biological features of their marineenvironment. We instrumented 15 SGP (six adults, nine juveniles) with satellite transmitters during81.4 ± 37 days at Isla Arce and Gran Robredo at the end of the breeding period. The seascape wascharacterized using environmental variables, oceanographic regimes, ocean surface winds, and prey(squid) distribution. Adult birds used 74% of the Argentine shelf concentrating mainly at the shelfbreak and middle shelf waters. They alternated at-sea excursions (12 ± 5 days) with periods at thecolony of 3 ± 0.3 days. Their environment lacked of thermal fronts, using depths of 100-200 m,exploiting mesotrophic environments, and remaining in areas related to the presence of squid.Juveniles spread to the Argentine, Uruguayan and Brazilian shelves moving first to the shelf breakand then traveling northwards to the south of Brazil. Spatial overlap between age classes was onlyregistered during the first 30 days after juveniles had fledged. Juveniles exploited a wide range ofenvironments focusing mainly on productive waters due to the presence of thermal fronts in theirutilization areas. The Argentine shelf offers a suitable environment for foraging; this may be whyadults SGP from Patagonia spend all year-round within the area. The identification of non breedingareas used by SGP fills a gap in the species knowledge. The understanding of pelagic birds´ habitatselection and preferences through the year is crucial for the monitoring and management ofanthropogenic impacts over these species