Olrog's Gull Larus atlanticus

  • Order: Charadriiformes
  • Family: Laridae
  • Monotypic
  • Authors: Pablo Yorio


Conservation Status

Olrog’s Gull is classified as Vulnerable (IUCN 2008) or “highly threatened” (Parker et al. 1996) and listed in Appendix I of the Convention on Migratory Species.

Effects of human activity on populations

Olrog’s Gull has a small range and total population size, with over 70 % of it concentrated in the Bahía Blanca estuary (Delhey and Petracci 2004, Yorio et al. 2005). This is an area subject to growing human pressure from urban development, industry, agriculture, recreation and fishing, which are resulting in increased pollution and habitat degradation (Yorio et al. 1997, Delhey et al. 2001b). Bahía Anegada, southern Buenos Aires, is also subject to recreational activities, artisanal fishing and ranching activities (Yorio et al. 2005). Harvesting of Olrog’s Gull eggs was common in the past at Bahía San Blas (Devillers 1977) and still occurs occasionally at Isla Arroyo Jabalí Oeste (Yorio et al. 2001, N. Suárez, pers. comm.). The effects of egging on this population have not been evaluated. In Chubut, different extractive activities occur in proximity to the colonies and may lead to human disturbance (Yorio et al. 1999). Along wintering areas in Buenos Aires province, tourism and recreation activities often result in human disturbance at feeding areas (Silva Rodriguez et al. 2005). Sports fisheries affect non-breeding birds in winter as a result of the ingestion of baited hooks, plastic bags and other waste disposed by fishermen (Berón et al. 2005).

All colonies in southern Buenos Aires, except the largest one, Isla del Puerto, are included in two protected areas: the Bahía Blanca, Falsa and Verde Nature Reserve and the Bahía San Blas Nature Reserve. The largest known colony containing more than half of the total breeding population of this threatened species, Isla del Puerto, has no legal protection (Delhey et al. 2001a). The colonies in southern Chubut have recently gained legal protection due to the designation of a new marine protected area in northern Golfo San Jorge, the Parque Interjurisdiccional Marino Costero Patagonia Austral. In winter, it has been recorded in numerous reserves (Chébez and Yorio 2008).

Preliminary studies show the presence of fecal pathogens such as Salmonella spp., Escherichia coli and Shigella spp. in the Olrog’s Gull (L. La Sala, P. Petracci and M. Uhart, unpubl. data).

Suggested conservation measures include (Yorio et al. 1999, Yorio et al. 2005): (1) Enlarge the Bahía Blanca, Falsa and Verde Nature Reserve to include the colony at Isla del Puerto, (2) Integrate management plans and actions through formal cooperative programs and (3) Develop joint conservation actions between Argentina and Uruguay within the current framework of international agreements.

Recommended Citation

Yorio, P. (2009). Olrog's Gull (Larus atlanticus), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.