The California scrub jay (Aphelocoma californica) is a species of scrub jay native to western North America. It ranges from southern British Columbia throughout California and western Nevada near Reno to west of the Sierra Nevada. The California scrub jay was once lumped with Woodhouse's scrub jay and collectively called the western scrub jay. IUCN and the Handbook of the Birds of the World maintain this lumped taxon. The group was also lumped with the island scrub jay and the Florida scrub jay; the taxon was then called simply scrub jay.

Range expansion

The California scrub jay's range has been expanding north over time. Although they were not seen at all during breeding bird surveys in Washington state in the early 1970s, by 2020 scrub jays are commonly found in the Puget Sound and even as far as British Columbia.

Foraging

California scrub jays usually forage in pairs, family groups, or small non-kin groups, outside of the breeding season. They feed on small animals, such as frogs and lizards, eggs and young of other birds, insects, and (particularly in winter) grains, nuts, and berries. They will also eat fruit and vegetables growing in backyards. Western scrub jays are also able to rely on their accurate observational spatial memories to steal food from caches made by conspecifics. Food-storing birds implement a number of strategies to protect their caches from potential 'pilferers.' Corvids have been observed taking acorns from acorn woodpecker caches. Some scrub jays snatch acorns from the hiding places of other jays. When these birds go to hide their own acorns, they check first that no other jays are watching. Other protection methods include moving the cache in the presence of an observer, storing inedible decoys like small stones instead of food, and hiding the cache once a scavenging bird is no longer watching; these behaviors are thought to vary based on the presence or absence of potential pilferers (like other corvids) as well as what kind of animal might pilfer the cache, implying strategic and socially complex motives behind different kinds of caching behavior.

Intelligence

Recent research has suggested that western scrub jays, along with several other corvids, are among the most intelligent of animals. The brain-to-body mass ratio of adult scrub jays rivals that of chimpanzees and cetaceans, and is dwarfed only by that of humans. Scrub jays are also the only non-primate or non-dolphin shown to plan ahead for the future (known as metacognition), which was previously thought of as a uniquely human trait.

Nesting

right|thumb|Juvenile in California, USA

Nests are built low in trees or bushes, above the ground, primarily by the female, while the male guards her efforts. The nests are sturdy, with an outside diameter of , constructed on a platform of twigs with moss and dry grasses lined with fine roots and hair. Four to six eggs are laid from March through July, with some regional variations. There are two common shell color variations: pale green with irregular, olive-colored spots or markings; and pale grayish-white to green with reddish-brown spots. The female incubates the eggs for about 16 days. The young leave the nest about 18 days after hatching.

Life span

The life span of wild California scrub jays is approximately 9 years. The oldest known western scrub jay was found in Castaic, California, in 1991 and raised in captivity. "Aaron" lived to be 19 years, and 8 months old.

Diseases

Populations are being adversely affected by the West Nile virus, particularly in California's Central Valley.

Phylogeny

thumb|California scrub jay showing the well-marked breast band of the coastal races

thumb|right|Note bright white plume breaking the breast band. Prominent markings in eye region are typical of male birds.

thumb|right|California scrub jay fledgling being fed

thumb|right|California scrub jay in flight

Woodhouse's, California, Island, and Florida scrub jay were once considered subspecies of a single "scrub jay" species. They are now believed to be distinct.

Further reading

  • Madge, Steve; Burn, Hilary (1994): Crows and jays: a guide to the crows, jays and magpies of the world. A&C Black, London. <small></small>
  • Western scrub jay Species Account – Cornell Lab of Ornithology
  • It takes a thief to know a thief – University of Cambridge Comparative Psychology of Learning and Cognition Lab article on studies of the cognitive abilities of western scrub jays (Archived on the Wayback Machine)