California Scrub-Jay

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''. The group was also lumped with the island scrub jay and the Florida scrub jay; the taxon was then called simply ''scrub jay''. The California scrub jay is nonmigratory and can be found in urban areas, where it can become tame and will come to bird feeders. While many refer to scrub jays as "blue jays", the blue jay is a different species of bird entirely.

Etymology

The generic name, ''Aphelocoma'', derives from Latinized Ancient Greek ''apheles-'' (from ἀφελής-) "simple" + Latin ''coma'' (from Greek ''kome'' κόμη) "hair", in reference to the lack of striped or banded feathers in this genus, compared to other jays. The species name, ''californica'', is Latin for "from California".

Description

The California scrub jay is a medium-sized bird, approximately in length (including its tail), with a wingspan, and about in weight. In general, this species has a blue head, wings, and tail; a gray-brown back; grayish underparts; and white eyebrows. The throat is whitish with a blue necklace. The call or "squawk" is described as "harsh and angry-sounding".

Behavior

Habitat

True to its name, the California scrub jay inhabits areas of low scrub, preferring pinyon-juniper forests, oak woods, and edges of mixed evergreen forests. It also inhabits suburban gardens.

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.

Food storing

California scrub jays, like many other corvids, exploit ephemeral surpluses by storing food in scattered caches within their territories. They rely on highly accurate and complex memories to recover the hidden caches, often after long periods of time. In the process of collecting and storing this food, they have shown an ability to plan ahead in choosing cache sites to provide adequate food volume and variety for the future. 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.'

Anecdotally, scrub jays – and corvids more generally – are known for an attraction to, and thievery of, brightly colored objects. Recent research debunks, or at least casts doubt, on this idea. Corvids do, however, have a mischievous streak, and scrub jays are not above outright theft. They have been observed stealing 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. Other studies have shown that they can remember locations of over 200 food caches, as well as the food item in each cache and its rate of decay. To protect their caches from pilfering conspecifics, scrub jays will choose locations out of sight of their competitors, or re-cache caches once they are alone, suggesting that they can take into account the perspective of others.

Jays are able to mimic raptors like red-tailed and red-shouldered hawks with such accuracy that is can be difficult to distinguish between species using calls alone; possible explanations for this behavior include warning other jays about the presence of a predator or trying to deter birds (like cache-pilfering corvids) from a given area. However, jays have been observed employing raptor-mimicking calls without the presence of other birds, making the precise adaptive reason for this behavior unknown, though it may be two-fold. California scrub jays also summon others to screech over the body of a dead jay, according to research from the University of California, Davis. The birds' cacophonous "funerals" can last for up to half an hour.

Nesting

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

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. Beyond the close relationship of the "California" and island scrub jays, resolution of their evolutionary history has proven very difficult.

Woodhouse's scrub jay differ in plumage (paler blue above, with an indistinct and usually incomplete breast band) from California scrub jay which is darker blue above with a strongly defined – but not necessarily complete – blue breast band.

The following subspecies are recognized:

References

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.

External links

Western scrub jay Species Account
– Cornell Lab of Ornithology


– 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)

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California scrub jay
Native birds of the Western United States
Fauna of the California chaparral and woodlands
Fauna of the San Francisco Bay Area
Birds of Mexico
California scrub jay
California scrub jay
California scrub jay
California scrub jay