Aphelocoma californica

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.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

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 .

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• desert or dune desert or dune
• savanna or grassland savanna or grassland
• forest forest

• Other Habitat Features
• suburban suburban

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.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

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.

• Mating System
• monogamous monogamous

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

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.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female parental care female parental care
• pre-fertilization
  • protecting
    • male
    • female
• pre-hatching/birth
  • provisioning
    • male
  • protecting
    • male

Lifespan/Longevity

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.

Behavior

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.

• Key Behaviors
• arboreal arboreal
• flies
• glides
• saltatorial saltatorial
• diurnal diurnal
• motile motile
• territorial territorial
• social social
• dominance hierarchies dominance hierarchies

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.

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.

• Communication Channels
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

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.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • eats eggs
  • insectivore insectivore
  • eats non-insect arthropods
• herbivore herbivore
  • frugivore frugivore
  • granivore granivore
• omnivore omnivore

• Animal Foods
• birds
• amphibians
• reptiles
• eggs
• insects
• terrestrial non-insect arthropods

• Plant Foods
• seeds, grains, and nuts
• fruit

• Foraging Behavior
• stores or caches food stores or caches food

Predation

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 .

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.

• Ecosystem Impact
• disperses seeds

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.

• Positive Impacts
• ecotourism 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.

• Negative Impacts
• injures humans
  • causes disease in humans causes disease in humans
  • carries human disease
• crop pest
• causes or carries domestic animal disease causes or carries domestic animal disease

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.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Jimmy Scott (author), Radford University, Karen Powers (editor), Radford University, Leila Siciliano Martina (editor), Texas State University.

References

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