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western scrub jay

Aphelocoma californica

What do they look like?

Western scrub-jays are usually 29.21 cm long, from the tip of their beak to the end of their tail. They can weigh between 70 to 100 g, although they average 85 g. Males of this species are usually bigger than females. These birds are brown, gray, white, and blue. They have fairly long beaks and tails. Their forehead is blue with white eyebrows and they have gray or black around their eyes. Their breast, sides, and belly are gray or white and the base of their neck is brown or black. On their wings, their primary and secondary feathers are blue. Western scrub-jays look different than other jay species because they do not have a crest or white on their wings, likewise, they are the only jays with their specific color combination. (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

Where do they live?

Western scrub-jays (Aphelocoma californica) are found in western North America. They can be found from the West Coast of the United States, north to northern Oregon, south to dry, southern areas of Mexico, and east to central Texas. These birds do not migrate, but during the winter months they may move to the lowland edges of their range. (Curry, 2002; Delaney, et al., 2008)

What kind of habitat do they need?

Western scrub-jays are often found in very dry, open, hot coastal areas. They are often found near large populations of humans. They can live up to 3,700 m in elevation, but they are usually found in lower elevation areas with thick grass and low shrubs. These birds are often found in dense forested areas. (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

How do they reproduce?

Western scrub-jays form monogamous breeding pairs, where each bird only mates with one other bird. To attract mates, males show off by preening their feathers, this involves using their bill to clean lice and other insects from their feathers. Preening helps them stay healthy and increases their chances of mating. Males usually establish a territory and build a nest in March. To court females, males sing a series of soft-pitched tones. (Clayton, 2002; Curry, 2002; Vleck and Brown, 1999)

Western scrub-jays breed from March to April. In many cases, these birds only have one brood per year, but if a brood is unsuccessful, they may try again. They usually lay 3 to 6 eggs that hatch in about 18 days. When they hatch, chicks usually weigh 5.6 to 7.5 g. After 16 to 26 days, western scrub-jays enter their fledgling stage, which means they are ready to leave the nest. These birds are physically ready to mate after about a year, however, until males are able to defend a territory, females will not mate with them, these males are considered 'floaters'. They can stay in their 'floating' stage for up to 7 years. (Carmen, 2004; Curry, 2002)

  • How often does reproduction occur?
    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

After a male finds a mate, he builds a nest before mating. Nests are made from plant material and twigs, as well as horse and cow hair. Females cover their chicks after they hatch. Nestlings usually eat moth or butterfly larvae and acorns. Males keep their nest clean by removing waste while the nestlings develop. (Curry, 2002)

How long do they live?

In the wild, the longest lifespan for this species is 15 years and 9 months, while in captivity, this species has survived up to 19 years and 8 months. A study in Monterey County, California found about 65% of birds survived their first year, but only 13% survived to their second year and only one bird lived past 5 years. (Clapp, et al., 1983; Linsdale, 1949; Vandersande, 2002)

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

How do they behave?

Western scrub-jays use a gliding flight, but move their wings more when they spot a prey item, or when they are trying to avoid a predator. When they are on the ground, western scrub-jays travel by hopping. Like other jays, these birds are diurnal, social, and rather vocal. Males defend territories during the breeding season and form social hierarchies based on the quality of their territory. When western scrub-jays find a dead member of their species, they call other jays to the spot by making loud calls. (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

Western scrub-jays keep 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)

How do they communicate with each other?

Western scrub-jays communicate in several ways. If they see a dead western scrub-jay on the ground, they react by flying from tree to tree and making loud screams, when they do this, other nearby western scrub-jays also begin vocalizing. They also have a specific vocalization for finding a mate. Western scrub-jays sing to possible mates in a sequence of tones with a soft pitch. Likewise, western scrub-jays use a specific call to defend their territory from an outsider. While resting on a branch, they make loud, repetitive screams from low to high pitch while raising their bill in the air. By using their sense of sight and smell, they are able to determine the food quality of the seeds they find. (Curry, 2002; Iglesias, et al., 2012)

What do they eat?

Western scrub-jays are omnivorous. Depending on the time of year, these birds eat plant or animal material. From October to February, they mostly eat acorns and from May to June they mostly eat fruit. They are most likely to eat animal matter during the month of April. Western scrub-jays eat 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 birds and their eggs, amphibians such as California slender salamanders, and reptiles such as western fence lizards. Depending on where they live, their bills have different shapes to help feeding. Jays found in areas with dense oak trees have deep, hooked bills, which helps them eat nuts. Jays found in areas with dense pinon pines have a more pointed bill, which helps them open pinon cones. They usually hide seeds in the ground, 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

What eats them and how do they avoid being eaten?

Western scrub-jays use high-pitched vocalizations when they feel threatened by 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)

What roles do they have in the ecosystem?

Western scrub-jays help disperse seeds throughout their habitats. They disperse seeds from a variety of oak, pine, and juniper species, specifically Colorado pinon pines, and bury them to eat them later. If, however, they do not return, the seeds have a chance to germinate. These jays also host lice species including Philopteras cassipes, Brueelia deficiens and Myrsidea species. Western scrub-jays form mutualistic relationships with Columbian black-tailed deer by eating ticks, hippoboscid flies (keds or louse flies), and deer flies from the deer's skin. (Bush, et al., 2009; Clayton, 2002; Francis, et al., 2012; Isenhart and Desante, 1985)

  • Ecosystem Impact
  • disperses seeds
Species (or larger taxonomic groups) that are mutualists with this species
  • Columbian black-tailed deer (Odocoileus hemionus columbianus)
Commensal or parasitic species (or larger taxonomic groups) that use this species as a host
  • lice (Philopteras cassipes)
  • lice (Brueelia deficiens)
  • lice (Myrsidea)

Do they cause problems?

Western scrub-jays can cause crop damage in fruit and pistachio orchards. They can also help spread West Nile virus. (Curry, 2002; Ladeau, et al., 2008)

How do they interact with us?

Humans often provide food for western scrub-jays, especially during winter months when less food is available. This can be pleasant for bird-watchers and beneficial to bird seed sales. These birds have also been researched to develop a better understanding of their role in their habitats. (Francis, et al., 2012; Jones and Reynolds, 2008)

  • Ways that people benefit from these animals:
  • ecotourism
  • research and education

Are they endangered?

Western scrub-jays currently have a stable population and are not endangered. However, 5,283 western scrub-jays have died over an 18-year period due to wind turbines. These jays are also found in areas with large populations of humans and domestic cats. Sadly, cats kill 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.


Bush, S., C. Harbison, D. Slager, A. Peterson, R. Price. 2009. Geographic variation in the community structure of lice on western scrub-jays. Journal of Parasitology, 95/1: 10-13.

Carmen, W. 2004. Noncooperative Breeding in the California Scrub-jay. Camarillo, CA: Cooper Ornithological Society.

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.

Curry, R. 2002. Western Scrub-jay: Aphelocoma californica. Philadelphia, Pa.: Birds of North America.

Delaney, K., Z. Saba, R. Wayne. 2008. Genetic divergence and differentiation within the western scrub-jay (Aphelocoma californica). The Auk, 125: 839-849.

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.

Isenhart, F., D. Desante. 1985. Observations of scrub jays cleaning ectoparasites from black-tailed deer. The Condor, 87: 145-147.

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

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.

University of Michigan Museum of ZoologyNational Science Foundation

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Scott, J. 2014. "Aphelocoma californica" (On-line), Animal Diversity Web. Accessed April 20, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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