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 GOMEZ-LAICH; FLAVIO QUINTANA

Cape Town

Congreso; 2nd World Seabird Conference; 2015

World Seabird Union and The African Seabird Group

The characterization of the seascape used by top predators helps to understand the functioning of marine systems. The main goals of this study were to 1) analyze habitat use and at-sea movements of adult and first year juvenile southern giant petrels (SGP, Macronectes giganteus) during the austral winter, and 2) to characterize the oceanographic and biological features of their marine environment. We instrumented 15 SGP (six adults, nine juveniles) with satellite transmitters during 81.4 ± 37 days at Isla Arce and Gran Robredo at the end of the breeding period. The seascape was characterized using environmental variables, oceanographic regimes, ocean surface winds, and prey (squid) distribution. Adult birds used 74% of the Argentine shelf concentrating mainly at the shelf break and middle shelf waters. They alternated at-sea excursions (12 ± 5 days) with periods at the colony 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 break and then traveling northwards to the south of Brazil. Spatial overlap between age classes was only registered during the first 30 days after juveniles had fledged. Juveniles exploited a wide range of environments focusing mainly on productive waters due to the presence of thermal fronts in their utilization areas. The Argentine shelf offers a suitable environment for foraging; this may be why adults SGP from Patagonia spend all year-round within the area. The identification of non breeding areas used by SGP fills a gap in the species knowledge. The understanding of pelagic birds´ habitat selection and preferences through the year is crucial for the monitoring and management of anthropogenic impacts over these species.