NT
Olrog's Gull Larus atlanticus



Taxonomy

Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
SACC. 2005 and updates. A classification of the bird species of South America. Available at: #http://www.museum.lsu.edu/~Remsen/SACCBaseline.htm#.

IUCN Red list criteria met and history
Red List criteria met
Critically Endangered Endangered Vulnerable
- - -

Red List history
Year Category Criteria
2018 Near Threatened B2b(iii)
2016 Near Threatened B2b(iii)
2013 Near Threatened B2b(iii)
2012 Vulnerable B1ab(ii,iii,v);C2a(i)
2008 Vulnerable B1a+b(ii,iii); C2a(i)
2006 Vulnerable
2004 Vulnerable
2000 Vulnerable
1996 Vulnerable
1994 Vulnerable
1988 Threatened
Species attributes

Migratory status full migrant Forest dependency Does not normally occur in forest
Land mass type Land-mass type - continent
Average mass -
Distribution

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 209,000 medium
Extent of Occurrence non-breeding (km2) 1,230,000 medium
Number of locations 6 -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 9800-15600 good estimated 2007
Population trend Stable poor suspected -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) - - -
Decline (10 years/3 generation past and future) - - -
Number of subpopulations 1 - - -
Percentage in largest subpopulation 100 - - -
Generation length (yrs) 11 - - -

Population justification: The breeding population is variable between years, with the total number of nests estimated at 4,860 pairs in 2004, 7,790 pairs in 2007 and 5,240 in 2009 (Yorio et al. 2013), roughly equating to 15,600 mature individuals.  The largest colony recorded is Isla del Puerto, with between 1,635 and 3,800 nests depending on the year (Petracci et al. 2008, Petracci and Sotelo 2013, Yorio et al. 2013).

Trend justification: The apparent population increase most likely reflects a more comprehensive simultaneous survey, and the variability between years in the observed total nesting population is over 20%, indicating the uncertainty involved and showing the difficulty in defining trends.  Nevertheless, despite growing pressures at key breeding sites there is no current evidence that the population is declining.


Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Argentina N Extant Yes
Brazil N Extant Yes
Chile U Extant
Uruguay N Extant Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Argentina Costa Bonita - Necochea
Uruguay Castillos Lagoon
Argentina Reserva Natural de Uso Múltiple Isla Martín García
Argentina Reserva Natural Punta Lara
Argentina Parque Costero del Sur
Argentina Bahía de Samborombón y Punta Rasa
Argentina Reserva de Biosfera Albufera de Mar Chiquita
Argentina Playa Punta Mogotes y Puerto de Mar del Plata
Argentina Reserva de Uso Múltiple de Bahía Blanca, Bahía Falsa y Bahía Verde
Argentina Reserva de Uso Múltiple San Blas y Refugio de Vida silvestre Complementario
Argentina Reserva Campos del Tuyú, Estancia El Palenque y Los Ingleses
Argentina Cuenca del Río Salado
Argentina Reserva de Uso Múltiple Bañados del Río Dulce y Laguna Mar Chiquita
Argentina Villa marítima El Cóndor
Argentina San Antonio Oeste
Uruguay José Ignacio Lagoon
Argentina Norte del Golfo San Jorge
Argentina Estuario del Río Gallegos
Uruguay Arroyo Maldonado wetlands
Argentina Península y Bahía de San Julián
Uruguay Penino Beach and Santa Lucía Wetlands
Uruguay Garzón Lagoon
Argentina Laguna Melincué
Brazil Estuário da Laguna dos Patos
Brazil Parque Nacional da Lagoa do Peixe
Argentina Confluencia, desembocadura y adyacencias de los ríos Chico y Santa Cruz
Argentina Boca albufera de Mar Chiquita
Argentina Cabo San Antonio
Argentina Isla del Puerto
Argentina Islas Zuraitas y Embudo
Argentina Isla Trinidad
Argentina Isla Gaviota
Argentina Isla Arroyo Jabalí Oeste
Argentina Banco Nordeste
Argentina Bahías Arredondo, Melo e islas
Argentina Punta Tafor e islas
Argentina Caleta Malaspina

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Marine Coastal/Supratidal Coastal Brackish/Saline Lagoons/Marine Lakes major non-breeding
Marine Intertidal Mud Flats and Salt Flats major non-breeding
Marine Intertidal Mud Flats and Salt Flats major breeding
Marine Intertidal Rocky Shoreline suitable non-breeding
Marine Intertidal Rocky Shoreline major breeding
Marine Intertidal Sandy Shoreline and/or Beaches, Sand Bars, Spits, Etc major breeding
Marine Intertidal Shingle and/or Pebble Shoreline and/or Beaches suitable non-breeding
Marine Intertidal Shingle and/or Pebble Shoreline and/or Beaches suitable breeding
Marine Intertidal Tidepools suitable non-breeding
Marine Intertidal Tidepools suitable breeding
Marine Neritic Macroalgal/Kelp major non-breeding
Marine Neritic Macroalgal/Kelp major breeding
Marine Neritic Pelagic marginal resident
Marine Neritic Seagrass (Submerged) major non-breeding
Marine Neritic Seagrass (Submerged) major breeding
Marine Neritic Subtidal Loose Rock/pebble/gravel major non-breeding
Marine Neritic Subtidal Loose Rock/pebble/gravel major breeding
Marine Neritic Subtidal Rock and Rocky Reefs major non-breeding
Marine Neritic Subtidal Rock and Rocky Reefs major breeding
Marine Neritic Subtidal Sandy suitable non-breeding
Marine Neritic Subtidal Sandy suitable breeding
Marine Neritic Subtidal Sandy-Mud major non-breeding
Marine Neritic Subtidal Sandy-Mud major breeding
Altitude   Occasional altitudinal limits  

Threats & impact
Threat (level 1) Threat (level 2) Impact and Stresses
Biological resource use Fishing & harvesting aquatic resources - Unintentional effects: (large scale) [harvest] Timing Scope Severity Impact
Ongoing Majority (50-90%) Slow, Significant Declines Medium Impact: 6
Stresses
Indirect ecosystem effects
Biological resource use Hunting & trapping terrestrial animals - Intentional use (species is the target) Timing Scope Severity Impact
Past, Likely to Return Majority (50-90%) Slow, Significant Declines Past Impact
Stresses
Species mortality
Pollution Industrial & military effluents - Type Unknown/Unrecorded Timing Scope Severity Impact
Ongoing Whole (>90%) Slow, Significant Declines Medium Impact: 7
Stresses
Ecosystem degradation, Reduced reproductive success
Residential & commercial development Commercial & industrial areas Timing Scope Severity Impact
Ongoing Majority (50-90%) Slow, Significant Declines Medium Impact: 6
Stresses
Ecosystem degradation, Ecosystem conversion
Residential & commercial development Housing & urban areas Timing Scope Severity Impact
Ongoing Minority (<50%) Slow, Significant Declines Low Impact: 5
Stresses
Ecosystem degradation, Ecosystem conversion
Residential & commercial development Tourism & recreation areas Timing Scope Severity Impact
Future Majority (50-90%) Slow, Significant Declines Low Impact: 4
Stresses
Ecosystem degradation, Ecosystem conversion

Utilisation
Purpose Primary form used Life stage used Source Scale Level Timing
Food - human - - Non-trivial Recent

Recommended citation
BirdLife International (2021) Species factsheet: Larus atlanticus. Downloaded from http://www.birdlife.org on 16/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/10/2021.