Data Zone
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.
| Critically Endangered | Endangered | Vulnerable |
|---|---|---|
| - | - | - |
| 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 |
| Migratory status | full migrant | Forest dependency | Does not normally occur in forest |
| Land mass type | Average mass | - |
| 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 | - |
| 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 | Occurrence status | Presence | Resident | Breeding | Non-breeding | Passage |
|---|---|---|---|---|---|---|
| Canada | N | Extant | Yes | |||
| Mexico | N | Extant | Yes | Yes | ||
| USA | N | Extant | Yes | Yes |
| 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 |
| 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 |
| 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.
