Animalia > Chordata > Aves > Charadriiformes > Laridae > Larus > Larus occidentalis

Larus occidentalis (Western Gull)

Language: Spanish

Wikipedia Abstract

The western gull (Larus occidentalis) is a large white-headed gull that lives on the west coast of North America. It was previously considered conspecific with the yellow-footed gull (Larus livens) of the Gulf of California. The western gull ranges from British Columbia, Canada to Baja California, Mexico, and, because of its convenient colonies on the coast of California, it is well studied. Despite being a well-known bird species on the West Coast of the US, it is of some slight conservation concern given its restricted range (for a gull).
View Wikipedia Record: Larus occidentalis


Larus occidentalis occidentalis (Western gull) (Attributes)
Larus occidentalis wymani (Western gull) (Attributes)

EDGE Analysis

Uniqueness Scale: Similiar (0) 
 Unique (100)
Uniqueness & Vulnerability Scale: Similiar & Secure (0) 
 Unique & Vulnerable (100)
ED Score: 1.54124
EDGE Score: 0.932654


Adult Weight [1]  2.05 lbs (932 g)
Birth Weight [1]  68 grams
Female Maturity [1]  5 years
Male Maturity [1]  4 years
Breeding Habitat [2]  Coastal cliffs and islands, Coastal marine
Wintering Geography [2]  Pacific Coast
Wintering Habitat [2]  Beaches and estuaries, Coastal marine
Diet [3]  Carnivore (Invertebrates), Carnivore (Vertebrates), Piscivore
Diet - Endothermic [3]  30 %
Diet - Fish [3]  30 %
Diet - Invertibrates [3]  20 %
Diet - Scavenger [3]  20 %
Forages - Ground [3]  80 %
Forages - Water Surface [3]  20 %
Clutch Size [1]  3
Clutches / Year [1]  1
Global Population (2017 est.) [2]  78,000
Incubation [1]  27 days
Maximum Longevity [1]  28 years
Wing Span [4]  4.5 feet (1.37 m)


Name Countries Ecozone Biome Species Report Climate Land
Baja California desert Mexico Nearctic Deserts and Xeric Shrublands
British Columbia mainland coastal forests Canada, United States Nearctic Temperate Coniferous Forests
California coastal sage and chaparral Mexico, United States Nearctic Mediterranean Forests, Woodlands, and Scrub
California interior chaparral and woodlands United States Nearctic Mediterranean Forests, Woodlands, and Scrub
California montane chaparral and woodlands United States Nearctic Mediterranean Forests, Woodlands, and Scrub
Central Pacific coastal forests Canada, United States Nearctic Temperate Coniferous Forests  
Klamath-Siskiyou forests United States Nearctic Temperate Coniferous Forests
Northern California coastal forests United States Nearctic Temperate Coniferous Forests
Puget lowland forests United States Nearctic Temperate Coniferous Forests

Protected Areas

Name IUCN Category Area acres Location Species Website Climate Land Use
Alto Golfo de California y Delta del Rio Colorado Biosphere Reserve VI 2320468 Sonora, Mexico  
Cabrillo National Monument V 149 California, United States
California Coast Ranges Biosphere Reserve 153447 California, United States  
Channel Islands National Marine Sanctuary   California, United States
Channel Islands National Park II 139010 California, United States
Elkhorn Slough Preserve Nature Conservancy - Preserve Ia 964 California, United States  
Farallon National Wildlife Refuge IV 352 California, United States
Golden Gate National Recreation Area V 26135 California, United States
Gulf Islands National Park National Park Reserve II 8785 British Columbia, Canada
Gwaii Haanas National Park Reserve II 366714 British Columbia, Canada
Lanphere-Christensen Dunes Preserve Nature Conservancy - Preserve Ia 471 California, United States  
Mojave and Colorado Deserts Biosphere Reserve 5901 California, United States  
Nipomo Dunes Preserve Nature Conservancy - Preserve Ia 3725 California, United States
Olympic Biosphere Reserve II 922805 Washington, United States
Pacific Rim National Park Reserve II 137900 British Columbia, Canada
Paine Preserve Nature Conservancy - Preserve 2965 California, United States    
Philip L. Boyd Deep Canyon Desert Research Center 6101 California, United States
Point Reyes National Seashore II 27068 California, United States
Redwood National Park II 77867 California, United States
Reserva de la Biosfera El Vizcaino Biosphere Reserve VI 6176727 Mexico  
San Juan Island National Historical Park III 1674 Washington, United States
Santa Cruz Island Preserve Nature Conservancy - Preserve 46021 California, United States
Santa Monica Mountains National Recreation Area V 38440 California, United States


Biodiversity Hotspots

Name Location Endemic Species Website
California Floristic Province Mexico, United States No
Mesoamerica Belize, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama No

Prey / Diet

Atherinops affinis (Topsmelt silverside)[5]
Atherinopsis californiensis (Jack silverside)[6]
Chilara taylori (Spotted cusk-eel)[6]
Citharichthys sordidus (Sanddab)[6]
Clupea pallasii (Pacific herring)[6]
Cololabis saira (Skipper)[7]
Cymatogaster aggregata (Shiner)[6]
Doryteuthis opalescens (california market squid)[6]
Engraulis anchoita (Anchoita)[8]
Engraulis australis (Australian anchovy)[8]
Engraulis capensis (Southern African anchovy)[8]
Engraulis encrasicolus (Southern African anchovy)[8]
Engraulis japonicus (Japanese anchovy)[8]
Engraulis mordax (Californian anchoveta)[7]
Glyptocephalus zachirus (Witch)[6]
Hemigrapsus oregonensis (yellow shore crab)[5]
Hippoglossus stenolepis (Pacific halibut)[8]
Kondakovia longimana (Giant Warty Squid)[8]
Merluccius productus (Whiting)[9]
Microgadus proximus (Tommy cod)[6]
Microstomus pacificus (Slippery sole)[6]
Myotis vivesi (fish-eating bat)[10]
Mytilus galloprovincialis (Mediterranean mussel)[5]
Pachygrapsus crassipes (striped shore crab)[5]
Pisaster ochraceus (Ochre sea star)[8]
Pleuroncodes planipes (pelagic red crab)[8]
Porichthys notatus (Midshipman)[6]
Puffinus opisthomelas (Black-vented Shearwater)[11]
Strongylocentrotus purpuratus (Purple sea urchin)[8]
Trachurus symmetricus (Scad)[7]
Zalembius rosaceus (Pink surfperch)[6]

Prey / Diet Overlap

Competing SpeciesCommon Prey Count
Alopias vulpinus (Zorro thresher shark)2
Anoplopoma fimbria (Skil)1
Ardea herodias (Great Blue Heron)1
Bathyraja trachura (Roughtail skate)1
Bucephala albeola (Bufflehead)1
Calidris mauri (Western Sandpiper)1
Callorhinus ursinus (Northern Fur Seal)2
Calonectris leucomelas (Streaked Shearwater)1
Cerorhinca monocerata (Rhinoceros Auklet)2
Charadrius semipalmatus (Semipalmated Plover)1
Clinocottus analis (Woolly sculpin)1
Corvus corax (Northern Raven)2
Delphinus delphis (Short-beaked Saddleback Dolphin)3
Egretta thula (Snowy Egret)3
Eschrichtius robustus (Gray Whale)1
Falco peregrinus (Peregrine Falcon)2
Fratercula cirrhata (Tufted Puffin)1
Gavia pacifica (Pacific Loon)1
Gillichthys mirabilis (Longjaw mudsucker)2
Katsuwonus pelamis (White bonito)1
Lagenorhynchus obliquidens (Pacific White-sided Dolphin)3
Lamna ditropis (Salmon shark)1
Lanius ludovicianus (Loggerhead Shrike)1
Larus canus (Mew Gull)4
Larus delawarensis (Ring-billed Gull)1
Larus livens (Yellow-footed Gull)1
Leptocottus armatus (Cabezon)2
Limosa fedoa (Marbled Godwit)2
Lissodelphis borealis (Northern Right Whale Dolphin)2
Lutjanus guttatus (mutton snapper)1
Melanitta perspicillata (Surf Scoter)1
Mirounga angustirostris (Northern Elephant Seal)2
Numenius americanus (Long-billed Curlew)2
Numenius phaeopus (Whimbrel)1
Nycticorax nycticorax (Black-crowned Night-Heron)1
Ophiodon elongatus (Lingcod)1
Orcinus orca (Killer Whale)1
Pandion haliaetus (Osprey)1
Paralabrax maculatofasciatus (Spotted sand bass)3
Phocoenoides dalli (Dall's Porpoise)2
Physeter macrocephalus (Sperm Whale)1
Pluvialis squatarola (Grey Plover)2
Procyon lotor (Raccoon)2
Puffinus bulleri (Buller's Shearwater)1
Puffinus griseus (Sooty Shearwater)2
Puffinus opisthomelas (Black-vented Shearwater)1
Raja rhina (Longnose skate)1
Sebastes caurinus (Copper rockfish)1
Seriphus politus (Drum)1
Thunnus alalunga (longfinned albacore)1
Thunnus thynnus (horse mackerel)1
Triakis semifasciata (Leopard shark)1
Tringa semipalmata (Willet)3
Tursiops truncatus (Bottlenosed Dolphin)2
Tyto alba (Barn Owl)1
Uria aalge (Common Murre)1
Zalophus californianus (California Sealion)3


Falco peregrinus (Peregrine Falcon)[8]


Parasitized by 
Acanthotrema hancocki[8]
Ceratophyllus pelecani[12]
Galactosomum humbargari[8]
Galactosomum puffini[13]
Himasthla rhigedana[8]
Parorchis acanthus[8]
Pygidiopsoides spindalis[8]

Institutions (Zoos, etc.)

Institution Infraspecies / Breed 
Project Wildlife

Range Map

North America; Oceania;



Attributes / relations provided by
1de Magalhaes, J. P., and Costa, J. (2009) A database of vertebrate longevity records and their relation to other life-history traits. Journal of Evolutionary Biology 22(8):1770-1774
2Partners in Flight Avian Conservation Assessment Database, version 2017. Accessed on January 2018.
3Hamish Wilman, Jonathan Belmaker, Jennifer Simpson, Carolina de la Rosa, Marcelo M. Rivadeneira, and Walter Jetz. 2014. EltonTraits 1.0: Species-level foraging attributes of the world's birds and mammals. Ecology 95:2027
4del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona.
5Lafferty, K. D., R. F. Hechinger, J. C. Shaw, K. L. Whitney and A. M. Kuris (in press) Food webs and parasites in a salt marsh ecosystem. In Disease ecology: community structure and pathogen dynamics (eds S. Collinge and C. Ray). Oxford University Press, Oxford.
6Szoboszlai AI, Thayer JA, Wood SA, Sydeman WJ, Koehn LE (2015) Forage species in predator diets: synthesis of data from the California Current. Ecological Informatics 29(1): 45-56. Szoboszlai AI, Thayer JA, Wood SA, Sydeman WJ, Koehn LE (2015) Data from: Forage species in predator diets: synthesis of data from the California Current. Dryad Digital Repository.
7Food Web Relationships of Northern Puget Sound and the Strait of Juan de Fuca : a Synthesis of the Available Knowledge, Charles A. Simenstad, Bruce S. Miller, Carl F. Nyblade, Kathleen Thornburgh, and Lewis J. Bledsoe, EPA-600 7-29-259 September 1979
8Jorrit H. Poelen, James D. Simons and Chris J. Mungall. (2014). Global Biotic Interactions: An open infrastructure to share and analyze species-interaction datasets. Ecological Informatics.
9Trophic Role of the Pacific Whiting, Merluccius productus, P. A. LIVINGSTON and K. M. BAILEY, Marine Fisheries Review 47(2), 1985, p. 16-22
10Myotis vivesi, Brad R. Blood and Mary K. Clark, MAMMALIAN SPECIES No. 588, pp. 1-5 (1998)
11Keitt, B.S., Tershy, B.R. & Croll, D.A. 2000. Black-vented Shearwater (Puffinus opisthomelas) In: Poole, A. & Gill, F. (Eds). The birds of North America. No. 521. Philadelphia & Washington, DC: Academy of Natural Sciences & the American Ornithologists’ Union.
12International Flea Database
13Gibson, D. I., Bray, R. A., & Harris, E. A. (Compilers) (2005). Host-Parasite Database of the Natural History Museum, London
Ecoregions provided by World Wide Fund For Nature (WWF). WildFinder: Online database of species distributions, ver. 01.06 WWF WildFINDER
Biodiversity Hotspots provided by Critical Ecosystem Partnership Fund
Images provided by Google Image Search
Abstract provided by DBpedia licensed under a Creative Commons License
Weather provided by NOAA METAR Data Access