Population trends of the Southern Rockhopper Penguin (Eudyptes chrysocome chrysocome) at the northern limit of its breeding range: Isla Pingüino, Santa Cruz, Argentina

During the last century, there has been a steady decline in the global breeding population of Eudyptes chrysocome chrysocome, and this species has been exposed to many different threats. However, the small breeding population of Isla Pingüino, Argentina, increased since its discovery in 1985 until 1990. To determine whether this population continued to grow, we assessed its trend over a 30-year period and estimated its breeding success. This study shows a strong increase in the population in Isla Pingüino with an annual growth rate of more than 7 %, throughout the 30-year study period. The threats that are affecting seabird populations in other areas seem to have no negative effects on this breeding population. In particular, tourism, which has grown exponentially during the survey period, appears to not have had a negative effect on the settlement of new pairs, the number of breeding pairs and their breeding success. We suggest that the population increase in Isla Pingüino might have been facilitated by an immigration of breeding adults from nearby breeding sites such as Falkland Islands (Malvinas).Fil: Gandini, Patricia Alejandra. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Centro de Investigaciones Puerto Deseado; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Millones, Ana. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Centro de Investigaciones Puerto Deseado; ArgentinaFil: Morgenthaler, Annick. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Centro de Investigaciones Puerto Deseado; ArgentinaFil: Frere, Esteban. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Centro de Investigaciones Puerto Deseado; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Uso diferencial del recurso alimento entre la gaviota cocinera Larus dominicanus y la amenazada gaviota de Olrog l. atlanticus

We assessed the potential overlap in diet composition of the kelp gull Larus dominicanus and the threatened Olrog's gull L. atlanticus breeding syntopically at Bahía San Blas, Argentina, during two breeding seasons (2006 and 2007). Diet was studied using regurgitated pellets (180 per species and year) and chick stomach samples obtained through the water offloading technique (60 per species only in 2007). Kelp gulls fed on at least 18 prey types. Fish was the most important diet component (73.3–85%, depending on breeding stage and year), mainly stripped weakfish Cynoscion guatucupa (63.3–75%). Crustaceans were the main prey encountered in Olrog's gull diet, particularly the crabs Neohelice granulata and Cyrtograpsus altimanus, with frequencies of occurrence of over 98% at all breeding stages. Fish in Olrog's gulls diet were only recorded in the old chick stage and in less than 3.3% of samples, while the occurrence of crustaceans in kelp gull diet throughout the study period was never greater than 13%. The specialised crab-based diet of Olrog's gulls contrasts sharply with the generalist and opportunistic diet of the kelp gull. The characteristics of prey remains and the large size of stripped weakfish found in kelp gull diet samples suggest they were obtained from coastal sport and artisanal fisheries. Future studies should monitor the consumption of fish waste by kelp gulls as a function of changes in fishing effort, and assess the dietary overlap between both gull species in coastal sectors where breeding birds have no access to this human-derived food source.Fil: Yorio, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Wildlife Conservation Society; Estados UnidosFil: Marinao, Cristian Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Retana, Maria Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Suarez, Nicolas Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin