Current status of the threatened Olrog's Gull Larus atlanticus: global population, breeding distribution and threats

Olrog's Gull Larus atlanticus breeds only in Argentina and is currently categorized as Vulnerable. Knowledge of the location of colonies and an updated understanding of human activities that may impact their breeding populations are crucial to the development of adequate conservation and management actions. In this paper we update the breeding distribution and abundance of Olrog's Gull, using information from three aerial surveys (2004, 2007 and 2009) in its main breeding area, Buenos Aires Province, complemented by additional nest counts in southern Chubut Province, covering its entire breeding range. We also provide an updated and more detailed account of threats faced by Olrog's Gulls at their nesting grounds, and summarise progress made towards their protection. The number of breeding sites was 7-12 per year, with locations differing among years. Five previously unrecorded breeding locations were identified. Colony size ranged from 5 to 3,540 breeding pairs, with the total breeding population 4,860-7,790 pairs, 98% of which nest in southern Buenos Aires Province. The main threats faced by breeding Olrog's Gulls include coastal development, pollution, sport fishing and unregulated tourism and recreational activities. Recent strengthening of the protected area system in Argentina has resulted in all known breeding sites, with the exception of Isla Brightman, falling within protected areas. We need comprehensive, simultaneous surveys to track global population trends. Despite enhanced protection of Olrog's Gull breeding populations, efforts are still needed to ensure that guidelines for their protection are included in management plans and that these are implemented effectively.Facultad de Ciencias Naturales y Muse

Does trampling by sheldgeese (Chloephaga spp.) cause soil compaction in wheat (Triticum aestivum) fields?

En Argentina los cauquenes (Chloephaga picta, Chloephaga poliocephala y Chloephaga rubidiceps) fueron declarados plaga nacional de la agricultura en 1931, impulsándose planes de control tendientes a reducir su abundancia. Sin embargo, debido a las declinaciones poblacionales documentadas, en la actualidad están declaradas a nivel nacional como Vulnerable, Amenazada y En Peligro de Extinción, respectivamente. Se cree que los cauquenes ocasionan pérdidas económicas por competir con el ganado doméstico por el recurso forrajero y por causar daños sobre cultivos de cereales, principalmente trigo. Además de sus efectos directos, el pastoreo por cauquenes podría tener efectos indirectos a través de la compactación del suelo. Este último efecto se evaluó midiendo la resistencia a la penetración en un cultivo de trigo con áreas pastoreadas por el Cauquén Común (Chloephaga picta) y sin pastoreo. La resistencia aumentó con la profundidad pero no mostró diferencias entre las áreas pastoreadas y las no pastoreadas. Bajo las condiciones estudiadas, el pisoteo por cauquenes no incrementó la compactación del suelo, indicando que no representaría un problema que justifique la implementación de medidas de control de estas especies en declinación numérica.Sheldgeese (Chloephaga picta, Chloephaga poliocephala y Chloephaga rubidiceps) have been considered a pest of agricultural croplands in Argentina since 1931, and different measures have been implemented to control their populations. However, these species have been listed as Vulnerable, Threatened, and Endangered, respectively, because of their reductions in population numbers. It has been suggested that they can impact the economy through grazing and the associated crop losses, especially on wheat. Beyond their potential direct effects, sheldgeese have also been traditionally held responsible for soil compaction through trampling. This idea was tested by comparing soil resistance to penetration in a wheat field in areas grazed and ungrazed by the Upland Goose (Chloephaga picta). Soil resistance increased with depth but no differences were found between grazed and ungrazed areas. Trampling by sheldgeese was not associated with soil compaction under the studied conditions, thus it would not represent a problem warranting the implementation of management strategies to control their population numbers.Facultad de Ciencias Naturales y Muse

Current status of the threatened Olrog's Gull Larus atlanticus: global population, breeding distribution and threats

Olrog's Gull Larus atlanticus breeds only in Argentina and is currently categorized as Vulnerable. Knowledge of the location of colonies and an updated understanding of human activities that may impact their breeding populations are crucial to the development of adequate conservation and management actions. In this paper we update the breeding distribution and abundance of Olrog's Gull, using information from three aerial surveys (2004, 2007 and 2009) in its main breeding area, Buenos Aires Province, complemented by additional nest counts in southern Chubut Province, covering its entire breeding range. We also provide an updated and more detailed account of threats faced by Olrog's Gulls at their nesting grounds, and summarise progress made towards their protection. The number of breeding sites was 7-12 per year, with locations differing among years. Five previously unrecorded breeding locations were identified. Colony size ranged from 5 to 3,540 breeding pairs, with the total breeding population 4,860-7,790 pairs, 98% of which nest in southern Buenos Aires Province. The main threats faced by breeding Olrog's Gulls include coastal development, pollution, sport fishing and unregulated tourism and recreational activities. Recent strengthening of the protected area system in Argentina has resulted in all known breeding sites, with the exception of Isla Brightman, falling within protected areas. We need comprehensive, simultaneous surveys to track global population trends. Despite enhanced protection of Olrog's Gull breeding populations, efforts are still needed to ensure that guidelines for their protection are included in management plans and that these are implemented effectively.Facultad de Ciencias Naturales y Muse

Granivorous habit in Olrog’s Gull (Larus atlanticus): implications for its specialist status

En este trabajo se dan a conocer observaciones sobre hábitos de alimentación desconocidos para la Gaviota Cangrejera (Larus atlanticus) en el puerto Ingeniero White, Bahía Blanca, Buenos Aires, Argentina. Entre 2002 y 2005, 281 individuos fueron observados alimentándose de granos en las banquinas del acceso y playa de estacionamiento del puerto. Los grupos de alimentación variaron entre 2–51 individuos. En el 78% de los casos este comportamiento ocurrió durante la pleamar, cuando el acceso a sus presas del intermareal era restringido. El uso de recursos de origen humano apoya la hipótesis que Larus atlanticus posee cierta plasticidad trófica y que puede comportarse como generalista. Se presenta una síntesis del estado actual del conocimiento de la dieta de esta especie y se propone una explicación para las distintas observaciones obtenidas a lo largo de la costa argentina.We report on unknown feeding habits of the Olrog’s Gull (Larus atlanticus) in the area of Ingeniero White port, Bahía Blanca, Buenos Aires Province, Argentina. Between 2002 and 2005, 281 individuals were observed feeding on grains along the shoulder of the road and in a parking lot besides the port. Feeding groups were of 2–51 individuals. This behaviour was observed mostly (78%) during high tides, when access to intertidal prey is limited. The exploitation of human resources by Larus atlanticus supports the hypothesis that this species has some degree of trophic plasticity and could behave as a generalist. We briefly review the literature on its diet, proposing an explanation for the different observations obtained along the coast of Argentina.Facultad de Ciencias Naturales y Muse

Presence of Cheirodon Interruptus in Valcheta stream, Río Negro province, Argentina

El arroyo Valcheta es una cuenca endorreica localizada en la provincia de Río Negro, Argentina. En este arroyo se conocen dos especies de vertebrados endémicas: la mojarra desnuda ( Gymnocharacinus bergii ) y la rana de Valcheta ( Pleurodema somuncurensis ), y dos especies endémicas de moluscos. La mojarra desnuda ( Gymnocharacinus bergii ) es una de las especies de peces de origen brasílico más austral y catalogado como especie en peligro en la lista roja de la UICN. Se realizaron muestreos en cinco sitios diferentes a lo largo del arroyo Valcheta y se reporta el primer registro del pez introducido Cheirodon interruptus (Characiformes: Characidae). Estudios previos de la dieta realizados en laboratorio muestran similitudes entre G. bergii y C. interruptus . Tomando como base este conocimiento previo, la existencia de interacciones negativas presentes y /o futuras en esos hábitats donde conviven ambas especies es altamente probable. Se discute el potencial efecto de esta población traslocada como una amenaza potencial para la especie endémica Gymnocharacinus bergii.The Valchet stream is an endorheic basin located in Río Negro province, Argentina. In this stream two species of endemic vertebrates are known: the Naked Characin (Gymnocharacinus bergii) and the Valcheta frog (Pleurodema somuncurensis), and two endemic mollusca species. The Naked Characin Gymnocharacinus bergii is one of the southernmost fish species with brassilic origin and listed as an endangered species by the IUCN red list. We performed surveys at five different sites along of the Valcheta stream and reported the first record of alien fish Cheirodon interruptus (Characiformes: Characidae). Previous diet studies in laboratory showed similarities between G. bergii and Cheirodon interruptus . Based on this background knowledge, the existence of present and/or future negative interactions in those habitats where both species live is highly probable. We discuss the potential effect of this exotic population as a potential threat to the endemic Gymnocharacinus bergii.Fil: Perez, Cristian Hernan Fulvio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Kacoliris, Federico Pablo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados. Sección Herpetologia; ArgentinaFil: López, Hugo Luis. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados; ArgentinaFil: Povedano, Emilio. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados; ArgentinaFil: Petracci, Pablo Fabricio. Secretaria de Ambiente y Desarrollo Sustentable; ArgentinaFil: Gosztonyi, Atila Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin

Update on the status of South American Sea Lion (Otaria flavescens) colony from Trinidad Island, Bahía Blanca estuary, Argentina.

El lobo marino de un pelo sudamericano ( Otaria flavescens ) se distribuye en la costa argentina desde Mar del Plata hasta Tierra del Fuego e Islas Malvinas con unas 70 colonias descriptas. En Buenos Aires existe una colonia reproductiva en Banco Culebra y tres no reproductivas en Mar del Plata, Quequén e Isla Trinidad. Esta última fue comunicada en 1952; desde ese año no se publicaron nuevos registros y en consecuencia la información citada posteriormente es confusa. En la presente nota se dan a conocer observaciones inéditas sobre su tamaño desde 1990. Se contaron entre 0 y 150 machos adultos y subadultos con variaciones según la época del año.The South American Sea Lion ( Otaria flavescens ) is distributed along the Argentinean coast, from Mar del Plata to Tierra del Fuego and Malvinas Islands, with 70 reporte colonies. In Buenos Aires there is one breeding colony in Banco Culebra and three non reproductive settlements in Mar del Plata, Quequén and Trinidad Island. The latter was reported for the first time in 1952, since then no further records were published about its current status and the information cited by many authors is confusing. Here we provide new observations about the population size of this colony from 1990. Seal counts ranged between 0-150 males and sub-adults depend- ing on the season.Facultad de Ciencias Naturales y Muse

Diet of the Kelp gull (Larus dominicanus) during the breeding season in the Bahía Blanca Estuary, Buenos Aires, Argentina

La Gaviota Cocinera (Larus dominicanus) está ampliamente distribuida en Argentina. Es una especie de comportamiento alimentario generalista y oportunista; según algunos autores, su capacidad de explotar recursos alimentarios derivados de actividades humanas ha favorecido su expansión geográfica. En este estudio se da a conocer la dieta de la Gaviota Cocinera durante el período reproductivo en una colonia de 3114 nidos ubicada en la Isla del Puerto, estuario de Bahía Blanca, provincia de Buenos Aires, Argentina. Se analizó un total de 1024 egagrópilas, cinco regurgitados de pichones y 12 de volantones, recolectados entre los meses de octubre y diciembre de 2003. Se registraron 39 categorías presa, de las cuales los granos (principalmente girasol) y la carroña de ganado vacuno tuvieron los mayores porcentajes en la dieta (54.6% y 29.0%, respectivamente). Ambos recursos están disponibles en grandes cantidades en las cercanías de la colonia, lo que podría estar favoreciendo el incremento poblacional observado en los últimos años. Otras presas halladas en la dieta, en orden decreciente de ocurrencia, fueron peces óseos, gasterópodos, insectos, cirripedios, basura, quitones, pelecípodos, roedores y otros. En la colonia de la Isla del Puerto, al igual que lo observado en otras colonias de la costa patagónica, la Gaviota Cocinera se comportaría como una especie generalista, con una fuerte tendencia a la explotación de recursos de origen humano y, en menor medida, de presas del ambiente marino costero.The Kelp Gull (Larus dominicanus) is widely distributed in Argentina. Several authors suggest that the species is expanding its geographic distribution due to its capacity to exploit food resources derived from human activities. This study shows the diet composition of the Kelp Gull during breeding season in a colony of 3114 nests located in the Del Puerto Island, Bahía Blanca estuary, Buenos Aires Province, Argentina. A total of 1024 pellets, five chick regurgitates, and 12 fledgling regurgitates collected between October and December 2003 were analyzed. A total of 39 prey categories were recorded, being grains (mainly sunflower) and cattle carrion the most important items (54.6% and 29.0%, respectively). These prey items are available in large quantities in the proximity of the colony, which could favour the population increase observed in the last years. Fishes, marine snails, insects, barnacles, garbage, chitons, mussels, clams, and rodents were also observed. Gulls from this colony, as in other colonies along the Patagonian coast, are generalists with a strong tendency to the exploitation of human-derived resources and, to a lesser degree, of seashore preys.Facultad de Ciencias Naturales y Muse

Does trampling by sheldgeese (Chloephaga spp.) cause soil compaction in wheat (Triticum aestivum) fields?

En Argentina los cauquenes (Chloephaga picta, Chloephaga poliocephala y Chloephaga rubidiceps) fueron declarados plaga nacional de la agricultura en 1931, impulsándose planes de control tendientes a reducir su abundancia. Sin embargo, debido a las declinaciones poblacionales documentadas, en la actualidad están declaradas a nivel nacional como Vulnerable, Amenazada y En Peligro de Extinción, respectivamente. Se cree que los cauquenes ocasionan pérdidas económicas por competir con el ganado doméstico por el recurso forrajero y por causar daños sobre cultivos de cereales, principalmente trigo. Además de sus efectos directos, el pastoreo por cauquenes podría tener efectos indirectos a través de la compactación del suelo. Este último efecto se evaluó midiendo la resistencia a la penetración en un cultivo de trigo con áreas pastoreadas por el Cauquén Común (Chloephaga picta) y sin pastoreo. La resistencia aumentó con la profundidad pero no mostró diferencias entre las áreas pastoreadas y las no pastoreadas. Bajo las condiciones estudiadas, el pisoteo por cauquenes no incrementó la compactación del suelo, indicando que no representaría un problema que justifique la implementación de medidas de control de estas especies en declinación numérica.Sheldgeese (Chloephaga picta, Chloephaga poliocephala y Chloephaga rubidiceps) have been considered a pest of agricultural croplands in Argentina since 1931, and different measures have been implemented to control their populations. However, these species have been listed as Vulnerable, Threatened, and Endangered, respectively, because of their reductions in population numbers. It has been suggested that they can impact the economy through grazing and the associated crop losses, especially on wheat. Beyond their potential direct effects, sheldgeese have also been traditionally held responsible for soil compaction through trampling. This idea was tested by comparing soil resistance to penetration in a wheat field in areas grazed and ungrazed by the Upland Goose (Chloephaga picta). Soil resistance increased with depth but no differences were found between grazed and ungrazed areas. Trampling by sheldgeese was not associated with soil compaction under the studied conditions, thus it would not represent a problem warranting the implementation of management strategies to control their population numbers.Facultad de Ciencias Naturales y Muse

Granivorous habit in Olrog’s Gull (Larus atlanticus): implications for its specialist status

En este trabajo se dan a conocer observaciones sobre hábitos de alimentación desconocidos para la Gaviota Cangrejera (Larus atlanticus) en el puerto Ingeniero White, Bahía Blanca, Buenos Aires, Argentina. Entre 2002 y 2005, 281 individuos fueron observados alimentándose de granos en las banquinas del acceso y playa de estacionamiento del puerto. Los grupos de alimentación variaron entre 2–51 individuos. En el 78% de los casos este comportamiento ocurrió durante la pleamar, cuando el acceso a sus presas del intermareal era restringido. El uso de recursos de origen humano apoya la hipótesis que Larus atlanticus posee cierta plasticidad trófica y que puede comportarse como generalista. Se presenta una síntesis del estado actual del conocimiento de la dieta de esta especie y se propone una explicación para las distintas observaciones obtenidas a lo largo de la costa argentina.We report on unknown feeding habits of the Olrog’s Gull (Larus atlanticus) in the area of Ingeniero White port, Bahía Blanca, Buenos Aires Province, Argentina. Between 2002 and 2005, 281 individuals were observed feeding on grains along the shoulder of the road and in a parking lot besides the port. Feeding groups were of 2–51 individuals. This behaviour was observed mostly (78%) during high tides, when access to intertidal prey is limited. The exploitation of human resources by Larus atlanticus supports the hypothesis that this species has some degree of trophic plasticity and could behave as a generalist. We briefly review the literature on its diet, proposing an explanation for the different observations obtained along the coast of Argentina.Facultad de Ciencias Naturales y Muse

New records of South American sea lion Otaria flavescens predation on southern rockhopper penguins Eudyptes chrysocome at Staten Island, Argentina

Predation by fur seals and sea lions has been identified, among others, as a potential cause of the declines in rockhopper penguin populations. Here, we report a multiple predation event of southern rockhopper penguins Eudyptes chrysocome by South American sub-adult male sea lions Otaria flavescens at Staten Island, Argentina. The sea lions attacked and preyed on penguins mostly using a wait and rush tactic at sea, but in some cases, penguins were also pursued on land. Although observations suggested that only a few sea lions are involved in predation, further research is necessary to elucidate the importance of this predation in the rate of population decline.Fil: Raya Rey, Andrea Nélida. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Saenz Samaniego, Ricardo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Petracci, Pablo Fabricio. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Área Zoología; Argentin