California gulls are North American birds. They are found in regions of Mexico, the west coast of the United States, the Great Plains, and western Canada. The species has been reported to live in California, Colorado, Kansas, Nevada, North Dakota, Oregon, Texas, Utah, Washington, and Wyoming. The birds are found in different regions depending on the season. In the summer, during breeding season, they are found in parts of northwestern Wyoming, northern Utah, western Nevada, and northern California. During the winter, California gulls can be observed on the Pacific coast from southern British Columbia to southern Mexico. The gulls migrate to North Dakota, British Columbia, lower California, and Monterey, California during the spring. In the fall the gulls migrate southwest to the coast in the states of Washington, Oregon, and California. (Bent, 1939; Winkler, 1996)
California gulls live in areas that contain lakes, marshes, and along the seacoast. They also reside on offshore islands, near rivers, agricultural land, and garbage dumps. When breeding, they often construct their nests near shrubs by bodies of water. (National Wildlife Federation, 2002; Small, 1994)
The average California gull is around 54 cm long and weighs about 600 g. While there are no differences in male and female plumage, males are usually larger than females, with a larger bill, head, and tarsi. When the bird is newly born it has a thick, soft down of light colors that blend in with the surrounding environment. By the juvenile's first winter, it has a brown mantle and wings, a brown head, and pink tinted legs. When the bird is around two years old the tail becomes white and the bill turns yellow. When the gull reaches its third year, it almost is completely like the adult in appearance, but the adult bill pattern and wing pattern are not completely developed. By the fourth winter the bird has an adult's white head, dark grey mantle, yellow green legs, reddish eye ring, and black wingtips. (Bent, 1939; Gough, et al., 1998; Winkler, 1996)
The young birds leave the territory of their parents forty to sixty days after they are born. By this time they are almost fully grown; however, feathers are still developing. The birds usually achieve their adult plumage and reach sexual maturity after four years. After leaving the parental colony, fledglings gather at the edge of water and swim together, usually forming groups at areas where substantial food is available. The ability of the birds to fly and feed improves to an adult level after around a month after they have left the territory of their parents.(Hobert, 2000; Winkler, 1996)
The "Head-Tossing Display" and the "Begging Call" are used to prompt copulation or courtship-feeding in California gulls. The ritual of courtship-feeding where the male bird delivers food to the female may occur during the pre-egg laying and early egg-laying stages. The "Head-Tossing Display" and "Begging Calls" can be used by either males or females to iniciate copulation. During copulation the male jumps onto the female's back and gives the "Copulation Call". Pairs usually remain together each breeding season, but in some cases partners change. (Winkler, 1996)
California gulls return to their home colony each year about three to seven weeks before they begin to lay their eggs. The breeding season occurs from May to July. Once a pair has formed, and the nest has been in the process of construction for around a week, egg laying begins. The birds lay one egg every other day until they have laid between two to five eggs. The eggs hatch after about 24 days and the chicks fledge within 40 to 60 days. A second brood is laid only if the first was unsuccessful. The birds usually build their nests close to shrubs by water sources such as marshes, ocean coasts, or lakes. Young birds reach sexual maturity after 4 years. (Bent, 1939; Winkler, 1996)
The male and female take turns incubating; the nonincubating parent guards the nest and hunts for food. In rare cases the chick will be smothered by the parent while it is trying to hatch because the parent is sitting too securely on the egg. Both parents feed the precocial offspring until they fledge. The parents swallow food, take it back to the nest, and regurgitate it in order to feed it to their young. (Winkler, 1996)
The lifespan of California gulls is usually between 4 and 24 years (20 on average). The oldest known California gull reached 30 years. Causes of death include exposure to cold weather, predation, parasitism, and competition with other species. (Winkler, 1996)
California gulls gather in groups of 2,000 to 40,000 birds. They breed while in these colonies. Young birds sometimes exhibit play behaviors, the most popular play action is picking up sticks, dropping them, and then picking them up again. This activity is expressed by young birds but almost never by adults.
While on land the birds walk and sometimes hop when moving to an elevated location. They run when they are about to take off for flight, but they are also able to jump directly into flight. Another form of locomotion for California gulls is swimming, which the birds do when catching aquatic prey. The birds also dive into water to capture their meals.
They preen their feathers with their bill and feet and they often preen while bathing. While bathing the gulls stretch their wings and shake off water to distribute it throughout the body.
California gulls spend about 10 to 20 percent of the day sleeping. The birds sleep on one leg, or sitting with their legs underneath the body. (Winkler, 1996)
We do not have information on home range for this species at this time.
Vocalized sounds serve as the main form of communication for California gulls. Young chicks use begging calls to let the parents know when they are hungry. As the birds get older the sounds increase in volume. When a predator enters the colony the gulls issue a warning call by dropping the pitch of the sound and stressing the second syllable. The mew call is a series of soft low notes used during courtship, courtship feeding, and copulation. When a mate returns to the nest to exchange duties with its partner, the mew call is also used. Furthermore, the mew sound is used in territorial conflicts. When the female gull wants her mate to feed her, the begging call is used. The copulation call is used solely by the male during copulation. California gulls use an alarm call of several sharp notes in response to the threat of a predator. When chasing or attacking a predator, the birds sound the charge call. If a bird is captured and struggling to escape, it emits the shrill waver, a hoarse thin call. (Bent, 1939; Winkler, 1996)
Members of this species also communicate through their posture. If a gull feels threatened, it holds its wings slightly away from its body. As a California gull prepares to attack, it gets into the lunge position. Pulling grass from the ground is another threat to other animals. Fights between individuals usually occur between two birds of the same sex. These physical demonstrations are often used along with calls. (Winkler, 1996) (Bent, 1939; Winkler, 1996)
Food preferences vary with the location of the bird's habitat. Favorite foods of California gulls include fish, birds, small mammals such as gophers and mice, garbage, insects, and aquatic invertebrates.
The birds use a range of different techniques to capture food. They often retrieve food such as fish near the surface of the water or brine shrimp by diving and pecking. The gulls capture small mammals like mice that have been flooded out of their holes by irrigation. In some instances the birds steal the eggs and chicks of other gulls in the colony. California gulls eat plant foods such as grains, vegetables, and especially cherries. The birds knock the cherries off the trees and then pick them up off the ground. They can also be found at garbage dumps dining on scraps of trash. (Bent, 1939; Winkler, 1996)
When a bird predator such as an eagle approaches the colony, the gulls respond with alarm and warning calls. When a coyote enters the colony, gulls may dive at it and sound warning calls. If a human comes into a gull colony the response will be even more severe. It is not uncommon for California gulls to attack humans by plunging at them.
Young gulls have cryptic coloration that helps to protect them from predators.
Known predators include: great horned owl (Bubo virginianus), golden eagle (Aquila chrysaetos), bald eagle (Haliaeetus leucocephalus), prairie falcon (Falco mexicanus), red-tailed hawk (Buteo jamaicensis), herring gull (Larus argentatus), red fox (Vulpes vulpes), weasel (family Mustelidae), feral dog (Canis lupus familiaris), muskrat (family Muridae), gopher snake (Pituophis melanoleucus), northern pike (Esox lucius), Canada goose (Branta canadensis), raccoon (Procyon lotor), skunk (family Mustelidae), river otter (Lontra canadensis) and other California gulls. (Winkler, 1996)
California gulls have an impact on the prey they consume.
California gulls are famous for reputedly aiding settlers in Salt Lake City, Utah, by eating the "locusts" (probably Mormon crickets, Anabrus simplex) that threatened their crops. California gulls benefit agriculturalists economically because they feed on the pests that destroy their crops, such as mice, and insects. Mouse holes often ruin crops, but as the fields are irrigated, mice are forced to come out of their holes and they are then eaten by the birds. Also, California gulls pick up trash along the edges of rivers and lakes, helping to keep areas free from garbage. (Bent, 1939; National Wildlife Federation, 2002)
While California gulls help farmers more often then not, recently they have caused problems by ravaging cherry crops. The birds beat the cherries off the trees and then collect and eat the fallen fruit from the ground. (Winkler, 1996)
The world-wide population of California gulls is somewhere between 500,000 and 1 million birds and growing. The gulls are not often killed by humans because they are usually appreciated for their benefits to agriculture. Occasionally gulls are killed by six-pack drink carriers which get caught around the gulls' necks when they feed on trash from garbage dumps. This can easily be prevented by cutting up the plastic before throwing it away.
California gulls are protected under the Migratory Bird Treaty Act, but are not listed by the IUCN, the US Federal List or CITES. (Winkler, 1996)
Alaine Camfield (editor), Animal Diversity Web.
Elizabeth Sherman (author), University of Michigan-Ann Arbor, Kerry Yurewicz (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
union of egg and spermatozoan
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
makes seasonal movements between breeding and wintering grounds
Having one mate at a time.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
an animal that mainly eats all kinds of things, including plants and animals
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
young are relatively well-developed when born
Bent, A. 1939. Life Histories of North American Gulls and Terns. Washington, D.C.: Washington Government Printing Office.
Gough, G., J. Sauer, M. Iliff. 1998. "Patuxent Bird Identification Infocenter" (On-line). Version 97.1. Patuxent Wildlife Research Center, Laurel, MD. Accessed 01/13/04 at http://www.mbr-pwrc.usgs.gov/Infocenter/infocenter.html.
Hobort, P. 2000. "Canada's Aquatic Environments" (On-line). Accessed 01/13/04 at http://www.aquatic.uoguelph.ca/birds/speciesacc/accounts/gulls/californ/account.htm.
National Wildlife Federation, 2002. "enature.com" (On-line). Accessed 01/13/04 at http://www.enature.com/fieldguide/showSpeciesGS.asp?sort=1&curGroupID=99&display=1&area=99&searchText=larus+californicus&curPageNum=1&recnum=BD0066.
Small, A. 1994. California Birds: Their Status and Distribution. Vista, California: Ibis Publishing Company.
Winkler, D. 1996. California gull : Larus californicus. The Birds of North America, 259: 1-27.