Aphelocoma californicawestern scrub jay(Also: western scrub-jay)

Geographic Range

Western scrub-jays (Aphelocoma californica) can be found in western portions of North America. They inhabit regions from central Texas, to the West Coast of the United States. They have been found as far north as northern Oregon and as far south as dry, southern areas of Mexico. Western scrub-jays generally do not migrate long distances. However, they may move outside of their described range to lowland areas on the edge of their range during winter months. (Curry, 2002; Delaney, et al., 2008)


Western scrub-jays can often be seen in very dry, open, hot coastal habitats. It is not uncommon to spot them in areas where human populations are dense. Although they inhabit elevations up to 3,700 m, western scrub-jays are more common in lower elevation areas with thick grass, brush, and low shrubs. They are often found in woodlands with a dense environment of oak trees and pinon pines. (Curry, 2002; Ramamoorthy, et al., 1993; Sibley, 2003; Woolfenden, 1985)

  • Range elevation
    0 to 3700 m
    0.00 to 12139.11 ft
  • Average elevation
    2000 m
    6561.68 ft

Physical Description

Western scrub-jays have, on average, a length of 29.21 cm from the tip of their beak to the end of their tail. Their average weight is 85 g; although adults can range from 70 to 100 g. Males are generally larger than females. Western scrub-jays are brown, gray, white, and blue. They have a relatively large bill and a long tail. These jays have a blue forehead streaked with white eyebrows and a mixture of gray and black around their eyes. Their breast, sides, and belly are gray or white and their mantle is brown or black. On their wings, their primary and secondary feathers are blue. Western scrub-jays can be distinguished from similar species by their lack of a crest, absence of white in their wings, and their distinct combination of a blue head, white breast, and brown back. (Curry, 2002; Sibley, 2003; Stokes, 2013)

  • Sexual Dimorphism
  • male larger
  • Range mass
    70 to 100 g
    2.47 to 3.52 oz
  • Average length
    29.21 cm
    11.50 in
  • Average wingspan
    39.37 cm
    15.50 in
  • Range basal metabolic rate
    2.8 to 4.9 cm3.O2/g/hr


Male western scrub-jays form a monogamous pair with a female. To attract a potential mate, western scrub-jays show off by preening. This preening is critical in maintaining healthy feathers and increasing mating success. Generally in March, male western scrub-jays establish their territory and build a nest specifically for breeding with a potential mate. To court them, males sing a sequence of tones with soft pitches to potential mates. (Clayton, 2002; Curry, 2002; Vleck and Brown, 1999)

Western scrub-jays participate in non-cooperative reproductive behavior. This means rather than staying closely associated with relatives in a group, jays reproduce outside of the family. Their breeding season occurs from March to April. The number of broods per season varies, depending on the success of each brood. Usually one brood is nested until it develops the ability to fly. If a brood is unsuccessful, western scrub-jays re-nest and try again with a second brood. On average, they raise one brood each year. Their nests usually include 3 to 6 eggs, which hatch in about 18 days. Their birth weight ranges from 5.6 to 7.5 g. After 16 to 26 days, western scrub-jays reach the fledgling stage, meaning they are able to leave the nest. Physically, western scrub jays reach sexually maturity after about 1 year; however, males must first be able to actively defend a territory for mating purposes, which may take up to 7 years. Western scrub-jays who are unsuccessful in defending a territory are termed "floaters." Floating may occur for up to 7 years before they successfully defend a territory, and thus, have something valuable to offer their mate. (Carmen, 2004; Curry, 2002)

  • Breeding interval
    Western scrub-jays breed once yearly.
  • Breeding season
    Western scrub-jays breed from March to April.
  • Range eggs per season
    3 to 6
  • Range time to hatching
    17 to 18 days
  • Average time to hatching
    18 days
  • Range fledging age
    16 to 26 days
  • Average fledging age
    20 days
  • Average time to independence
    20 days
  • Range age at sexual or reproductive maturity (female)
    1 (low) years
  • Range age at sexual or reproductive maturity (male)
    1 (low) years

Once a breeding pair becomes established, male western scrub-jays construct their nest before sexual reproduction. The materials used for nest construction include plant materials and twigs, as well as horse and domestic cow hair. Females cover the chicks after they have hatched. The typical nestling diet includes moth or butterfly larvae and acorns. The cleanliness of the nest is maintained by the male, who removes fecal matter from the nest during nestling development. (Curry, 2002)


The longest recorded lifespan for western scrub-jays in the wild is 15 years and 9 months, while the record in captivity is 19 years and 8 months. A study of winter migrants in Monterey County, California completed a mark-and-recapture study over a period of 11 years. They found survivorship rates were high in the first year (65%), but dropped substantially afterward. Although 13% lived to age 2, just one bird tracked (2% of the sample) survived until age 5. (Clapp, et al., 1983; Linsdale, 1949; Vandersande, 2002)

  • Range lifespan
    Status: wild
    15.75 (high) years
  • Range lifespan
    Status: captivity
    19.67 (high) years


During flight, western scrub-jays use repetitive wing-beats that alternate with a gliding flight. They increase the speed of their wing-beats during predator or prey interactions to maintain a specific level of flight in the air. Western scrub-jays travel by hopping while on the ground. Like other jays, these birds are diurnal, social, and rather vocal. Males defend territories during the breeding season and form lose hierarchies based on territory quality. When a member of this species discovers a dead conspecific, they summon other jays to the area by making loud calls. The death of a conspecific also affects their foraging capacity temporarily. (Carmen, 2004; Curry, 2002; Iglesias, et al., 2012; Sibley, 2003)

  • Range territory size
    6600 to 65000 m^2
  • Average territory size
    25300 m^2

Home Range

Studies of their territories reveal an average territory size of 25.3 ha, with a minimum size of 0.66 ha and a maximum size of 65 ha. (Curry, 2002; Sibley, 2003)

Communication and Perception

Western scrub-jays communicate in a variety of ways. If they see a deceased western scrub-jay on the ground, they react by flying from tree to tree and making vocalized screams that rise very rapidly and repetitively from low to high pitch. This behavior causes other western scrub-jays in the immediate area to make the same vocalizations. They also have a specific vocalization for identifying a potential mate. Western scrub-jays sing to potential mates in a sequence of tones with a soft pitch. Likewise, western scrub-jays use a distinctive call to defend their territory from an intruder. While resting on a branch, they produce a scream, which sounds similar to the vocalizations made in reaction to a deceased conspecific. They make loud, repetitive screams from low to high pitch while raising their bill in the air and projecting to the intruder. By using their sense of sight and smell, they are able to differentiate food quality between each seed they encounter. (Curry, 2002; Iglesias, et al., 2012)

Food Habits

Western scrub-jays are considered omnivorous. Their diet consists of a diverse range of animal and plant material, which varies based on the time of year. These birds consume mostly acorns from October to February and mostly fruit from May to June. They consume the largest quantity of animal matter during the month of April. Western scrub-jays consume fruits, mainly cherries and prunes, as well as other grains and vegetables such as oats and corn. These birds also eat insects including beetles, bees, moths, grasshoppers, and planthoppers. Western scrub-jays may prey on animals including small land birds and their eggs, amphibians such as California slender salamanders, and reptiles such as western fence lizards. These jays have evolved structures that have enabled them to feed more efficiently. One structure is the base of their mandible, which allows them to whip snakes and caterpillars onto the ground. Their bill has evolved into different shapes depending on their feeding habit. Jays located in habitats with dense oak trees have deep, hooked bills, which enable them to consume nuts more efficiently. Jays located in habitats with dense pinon pines have a more pointed bill, which allows them to penetrate pinon cones for increased nut consumption. They prefer to store seeds in the ground for later use, but they may also hide them under rocks or on top of telephone poles and cover them with leaves. (Clayton, 2002; Curry, 2002; Dunn and Tessaglia-Hymes, 1999)

  • Animal Foods
  • birds
  • amphibians
  • reptiles
  • eggs
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • seeds, grains, and nuts
  • fruit


Western scrub-jays use high-pitched vocalizations when they perceive larger predators such as raccoons, long-tailed weasels, western spotted skunks, striped skunks, western gray squirrels, fox squirrels and a host of snake and bird species. Common avian predators include American crows, Cooper's hawks, sharp-shinned hawks, golden eagles, red-tailed hawks, and prairie falcons. (Clayton, 2002; Curry, 2002)

Ecosystem Roles

Western scrub-jays help maintain ecosystems through seed dispersal. They disperse seeds from a variety of oak, pine, and juniper species, specifically Colorado pinon pines, and bury them with the intention of eating them later. If, however, the jay does not return, the seeds have a chance to germinate. These jays also host ectoparasites such as lice. Three lice ectoparasites are known to be host-specific to western scrub-jays and include Philopteras cassipes, Brueelia deficiens and Myrsidea species. These jays also establish mutualistic relationships with Columbian black-tailed deer by eating ticks, hippoboscid flies (keds or louse flies), and flies from family Tabanidae (deer flies) from the skin of the deer. (Bush, et al., 2009; Clayton, 2002; Francis, et al., 2012; Isenhart and Desante, 1985)

  • Ecosystem Impact
  • disperses seeds
Mutualist Species
  • Columbian black-tailed deer (Odocoileus hemionus columbianus)
Commensal/Parasitic Species
  • lice (Philopteras cassipes)
  • lice (Brueelia deficiens)
  • lice (Myrsidea)

Economic Importance for Humans: Positive

Western scrub-jays are often fed from human-maintained feeders, especially during winter months when food is less abundant. This is potentially pleasant for bird-watchers and beneficial to bird seed sales. Experimentation and research on western scrub-jays has also been carried out to help humans gain an understanding of their ecological roles and the negative effects of anthropogenic noise on ecology. (Francis, et al., 2012; Jones and Reynolds, 2008)

  • Positive Impacts
  • ecotourism
  • research and education

Economic Importance for Humans: Negative

Western scrub-jays have a preference for fruits, nuts, and a variety of vegetables, causing crop production to suffer, particularly in fruit and pistachio orchards. These jays can also serve as an amplifying host for West Nile virus. The virus can be transferred from the jays to humans through mosquito bites. (Curry, 2002; Ladeau, et al., 2008)

Conservation Status

Populations of western scrub-jays are currently being maintained and the species is not endangered, however, potential long-term threats to western scrub-jays exist. For example, 5,283 western scrub-jays have died in an 18-year period as a result of wind turbines. These jays also frequent habitats where populations of humans and domestic cats are dense. Unfortunately, cats are responsible for the death of billions of birds in the United States every year. (Curry, 2002; Milius, 2013)


Jimmy Scott (author), Radford University, Karen Powers (editor), Radford University, Leila Siciliano Martina (editor), Animal Diversity Web Staff.



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.

World Map


uses sound to communicate


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

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.


an animal that mainly eats meat

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal


uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates


humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.


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.

female parental care

parental care is carried out by females


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


an animal that mainly eats fruit


an animal that mainly eats seeds


An animal that eats mainly plants or parts of plants.


An animal that eats mainly insects or spiders.


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).

male parental care

parental care is carried out by males


Having one mate at a time.


having the capacity to move from one place to another.

native range

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.


specialized for leaping or bounding locomotion; jumps or hops.

seasonal breeding

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.

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"


living in residential areas on the outskirts of large cities or towns.


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

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


uses sight to communicate


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Clapp, R., M. Klimkiewicz, A. Futcher. 1983. Longevity records of North American birds: Columbidae through Paridae. Journal of Field Ornithology, 54/2: 123-137.

Clayton, D. 2002. Influence of bill shape on ectoparasite load in western scrub-jays. The Condor, 104: 675-678.

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Dunn, E., D. Tessaglia-Hymes. 1999. Birds at Your Feeder. New York City, NY: W. W. Norton & Company.

Francis, C., N. Kleist, C. Ortega, A. Cruz. 2012. Noise pollution alters ecological services: Enhanced pollination and disrupted seed dispersal. The Royal Society, 279: 2727-2735.

Iglesias, T., R. McElreath, G. Patricelli. 2012. Western scrub-jay funerals: Cacophonous aggregations in response to dead conspecifics. Animal Behaviour, 84/5: 1103-1111.

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Jones, D., S. Reynolds. 2008. Feeding birds in our towns and cities: a global research opportunity. Journal of Avian Biology, 39: 265-271.

Ladeau, S., P. Marra, K. A, C. Calder. 2008. West Nile virus revisited: Consequences for North American ecology. Bioscience, 58/10: 937-946.

Linsdale, J. 1949. Survival in birds banded at the Hastings Reservation. The Condor, 51/2: 88-96.

Milius, S. 2013. Cats claim billions of bird and small mammal victims annually. Science News, 183/4: 14.

Ramamoorthy, T., R. Bye, A. Lot. 1993. Biological Diversity of Mexico: Origins and Distribution. New York, NY: Oxford University Press.

Sibley, D. 2003. The Sibley Field Guide to Birds. New York, United States: Alfred A. Knopf, Inc.

Stokes, D. 2013. The New Stokes Field Guide to Birds Western Region. New York, NY: Little, Brown and Company Hachette Book Group.

Vandersande, E. 2002. "This Bluejay is no Bluejay" (On-line). Accessed November 13, 2013 at http://scvnews.com/2013/02/14/this-blue-jay-is-no-blue-jay-commentary-by-evelyne-vandersande/.

Vleck, C., J. Brown. 1999. Testosterone and social and reproductive behaviour in Aphelocoma jays. Animal Behaviour, 58: 943-951.

Woolfenden, G. 1985. The Florida Scrub Jay: Demography of a Cooperative-breeding Bird. Princeton, NJ: Princeton University Press.