LC
Western Gull Larus occidentalis



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.

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

Red List history
Year Category Criteria
2018 Least Concern
2016 Least Concern
2012 Least Concern
2009 Least Concern
2008 Least Concern
2004 Least Concern
2000 Lower Risk/Least Concern
1994 Lower Risk/Least Concern
1988 Lower Risk/Least Concern
Species attributes

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

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 656,000 medium
Extent of Occurrence non-breeding (km2) 1,400,000 medium
Number of locations -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals poor estimated 2009
Population trend Increasing 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 - - -
Percentage in largest subpopulation - - -
Generation length (yrs) 12.8 - - -

Population justification: The global population has been estimated at between 115,500 and 118,500 individuals (Delany and Scott 2009).

Trend justification: The overall population trend is increasing, although some populations have unknown trends (Delany and Scott 2009). This species has undergone a small or statistically insignificant increase over the last 40 years in North America (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007).


Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Canada N Extant Yes
Mexico N Extant Yes Yes
USA N Extant Yes Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
USA Goat Island NWR
USA Castle Rock
USA Channel Islands North
USA False Cape Rock
USA False Klamath
USA Farallon Islands
USA Point Reyes - Outer
USA Santa Barbara Island - CA215
USA Trinidad Complex
USA Santa Cruz Basin 120W34N
USA Newport
USA Heceta Bank
USA Farallon Islands Pelagic
USA Santa Barbara Island, CA
USA Santa Barbara Basin, CA
Mexico Isla San Jerónimo
Mexico Isla Natividad
Mexico Archipiélago San José
Mexico Islas San Benito
USA Santa Cruz Basin 120W33N
USA Yaquina Head Outstanding Natural Area
USA Marbled Murrelet IBA
Mexico Isla Asunción
Mexico Isla San Roque
Mexico Bahía Magdalena-Almejas
Mexico Complejo Lagunar Ojo de Liebre
Mexico Islas Coronado
Mexico Área de San Quintín

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Marine Coastal/Supratidal Sea Cliffs and Rocky Offshore Islands major breeding
Marine Intertidal Rocky Shoreline suitable non-breeding
Marine Intertidal Rocky Shoreline suitable breeding
Marine Intertidal Sandy Shoreline and/or Beaches, Sand Bars, Spits, Etc suitable non-breeding
Marine Intertidal Sandy Shoreline and/or Beaches, Sand Bars, Spits, Etc suitable breeding
Marine Intertidal Shingle and/or Pebble Shoreline and/or Beaches major 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 suitable non-breeding
Marine Neritic Pelagic suitable breeding
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 major non-breeding
Marine Neritic Subtidal Sandy major breeding
Marine Neritic Subtidal Sandy-Mud major non-breeding
Marine Neritic Subtidal Sandy-Mud major breeding
Altitude   Occasional altitudinal limits  

Utilisation
Purpose Primary form used Life stage used Source Scale Level Timing
Pets/display animals, horticulture - - International Non-trivial Recent

Recommended citation
BirdLife International (2022) Species factsheet: Larus occidentalis. Downloaded from http://www.birdlife.org on 28/06/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 28/06/2022.