Habitat use of a threatened gull: the Olrog?s Gull (Larus atlanticus) in Mar Chiquita Lagoon, Argentina

RAVASI T.; COPELLO S.; SECO PON J.P.; PAZ J.; FAVERO M.

Conferencia; Second World Seabird Conference; 2015

Olrog?s Gull Larusatlanticus is endemic to the Atlantic coast of southern South America andis currently listed as Near Threatened. The species breeds in estuaries inPatagonia and, during winter, migrate northwards as far as southern Brazil. Duringthe breeding season the species is considered to have a specialized dietforaging mostly on crabs. However, during the non-breeding season gullspresents a wider spectrum (which includes fish) as result of a possibleassociation with commercial and sport fishing. The main goal of this study wasto analyze the habitat use of juvenile Olrog?s Gull in one of the mostimportant wintering areas (Mar Chiquita Lagoon, Argentina). Seventeen GPS devices(CatTraQ live 3) were deployed during the winters of 2013 and 2014. A total of1088 fixes were gathered by GSM (both seasons combined). A kernel analysisshowed that the individuals were chiefly (95% contour area) distributed in alimited area along the mouth of the lagoon of 13 km2. The core area (kernel 50%) coveredonly 2 km2 and was located in the South of the mouth. The mostimportant area of bird? distributions was characterized by high crab densityand as well as concentration of sport fishing activities. No locations were observed in offshore areas andonly one individual covered a distance of 43 km to the north of the mouth. In a largeproportion of individuals (65%), the core areas were overlapped each other inareas of the Lagoon´s mouth. For the rest of the gulls the core areas were locatedfurther north and in subsidiary creeks. These results are of value for the furtherdeveloping marine conservation measures for wintering areas so far somewhatneglected while addressing the conservation status of the species.