• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

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: https://www.museum.lsu.edu/~Remsen/SACCBaseline.htm.

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

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	209,000 km2	medium
Extent of Occurrence (non-breeding)	1,230,000 km2	medium
Number of locations	6	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	9800-15600 mature individuals	good	estimated	2007
Population trend	stable	poor	suspected	1975-2008
Generation length	11 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

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	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Argentina	extant	native		yes
Brazil	extant	native			yes
Chile	extant	uncertain
Uruguay	extant	native			yes

Country/Territory	IBA Name
Argentina	Albufera de Mar Chiquita
Argentina	Bahía Blanca, Bahía Falsa y Bahía Verde
Argentina	Bahía Samborombón
Argentina	Bahía San Blas, Bahía Anegada y Bahía Unión
Argentina	Costa Bonita - Necochea
Argentina	Cuenca del Río Salado
Argentina	Laguna Melincué
Argentina	Parque Costero del Sur
Argentina	Playa Punta Mogotes y Puerto de Mar del Plata
Argentina	Reserva de Uso Múltiple Bañados del Río Dulce y Laguna Mar Chiquita
Argentina	Reserva Natural de Uso Múltiple Isla Martín García
Argentina	Reserva Natural Punta Lara
Uruguay	Arroyo Maldonado wetlands
Uruguay	José Ignacio Lagoon
Uruguay	Penino Beach and Santa Lucía Wetlands

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

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

Purpose	Scale
Food - human	subsistence, national

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Recommended citation
BirdLife International (2024) Species factsheet: Olrog's Gull Larus atlanticus. Downloaded from https://datazone.birdlife.org/species/factsheet/olrogs-gull-larus-atlanticus on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 23/11/2024.