Western scrub jay

Western scrub jay
"California" Western scrub jay in Seattle, Washington.
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Corvidae
Genus: Aphelocoma
Species: A. californica
Binomial name
Aphelocoma californica
(Vigors, 1839)
Subspecies

14 (7+7) – see text

The western scrub jay (Aphelocoma californica), [A] is a species of scrub jay native to western North America. It ranges from southern Washington to central Texas and central Mexico. It comprises three distinct subspecies groups, all of which may be separate species. They are California scrub jay (coastal), Woodhouse's scrub jay (interior US and northern Mexico), and Sumichrast's scrub jay (interior southern Mexico). The western scrub jay was once lumped with the island scrub jay and the Florida scrub jay; the taxon was then called, simply, the scrub jay.[2] The western 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. In recent years, the California scrub jay has expanded its range north into the Tsawwassen region of British Columbia.

Description

The western scrub jay is a medium-sized bird, approximately 27–31 cm (11–12 in) in length (including its tail), with a 39 cm (15 in) wingspan, and about 80 g (2.8 oz) in weight. Coastal Pacific birds tend to be brighter in coloration than those of the interior, but all are patterned in blue, white and gray, though none as uniform in color as the related Mexican jay. In general, this species has a blue head, wings, and tail, a gray-brown back, and grayish underparts. The throat is whitish with a blue necklace. The call is described as "harsh and scratchy".

Habitat

True to its name, the western scrub jay inhabits areas of low scrub, preferring pinon-juniper forests, oak woods, edges of mixed evergreen forests and sometimes mesquite bosques. The coastal population also inhabits suburban gardens. Western scrub jays are very common west of the Rocky Mountains, and can be found in scrub-brush, boreal forests, temperate forests, coastal regions, and suburban areas.

Foraging

Western 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 can be aggressive towards other birds, for example, they have been known to steal hoarded acorns from Acorn Woodpecker granary trees. They will also eat fruit and vegetables growing in backyards.

Food storing

Western 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.[3] 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.[4] Western scrub jays are also able to rely on their accurate observational spatial memories to steal food from caches made by conspecifics. To protect their caches from potential 'pilferers', food storing birds implement a number of strategies to reduce this risk of theft.[5][6] Western scrub jays are also known for hoarding and burying brightly colored objects. Western scrub jays have a mischievous streak, and they are not above outright theft. They have been caught stealing acorns from acorn woodpecker caches and robbing seeds and pine cones from Clark's nutcrackers. Some scrub jays steal acorns they have watched other jays hide. When these birds go to hide their own acorns, they check first that no other jays are watching. You might see western scrub jays standing on the back of a mule deer. They’re picking off and eating ticks and other parasites. The deer seem to appreciate the help, often standing still and holding up their ears to give the jays access. The scrub jay even will eat peanuts off a human hand.

Intelligence

Main article: Bird 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, which was previously thought of as a uniquely human trait.[7] 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.[8] Western scrub jays also summon others to screech over the body of a dead jay, according to new research from the University of California, Davis. The birds' cacophonous "funerals" can last for up to half an hour.[9]

Nesting

Juvenile in California, USA

The chicks start off fully gray. The older they get, the more they turn blue. On their heads, chicks tend to have a red crest that resembles a comb (Mostly seen on chickens). The chick will lose its crest at day seven, just like the way the baby chickens lose their egg tooth at 5–7 days. Nests are built low in trees or bushes, 1–10 m (3.3–32.8 ft) above the ground, primarily by the female, while the male guards her efforts. The nests are sturdy, with an outside diameter of 33–58 cm (13–23 in), 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 western scrub jays is approximately 9 years. The oldest known western scrub jay was found in Castaic, CA, 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

The Western, Island, and Florida scrub jay were once considered subspecies of a single "scrub jay" species. They are now believed to be distinct.[2][10][11] Beyond the close relationship of the "California" and island scrub jays, resolution of their evolutionary history has proven very difficult.

Judging from mtDNA NADH dehydrogenase subunit 2 sequence data, it appears there are two clades, namely a Pacific one west and one east of the Rocky Mountains; the relationships of populations in the latter are not resolvable to satisfaction.[11][11] Thus, it is fairly likely the western scrub jay is actually another two distinct species, one belonging to the Pacific and another one to the eastern lineage(s); the latter's ancestors apparently gave rise to the Florida scrub jay as well. Paleogeography of the Rocky Mountains range supports this scenario.

Inland birds (Woodhouse's scrub jay, woodhouseii group and Sumichrast's scrub jay, sumichrasti group) differ in plumage (paler blue above, with an indistinct and usually incomplete breast band) from the coastal birds (California scrub jay, californica group) which are darker blue above with a strongly defined – but not necessarily complete – blue breast band. The three groups also differ in ecology and behavior. The beaks of the California and Sumichrast's groups are strong and hooked at the tip, as they feed on acorns, whereas the pinyon-nut feeding Woodhouse's group has a longer, slimmer and straighter bill with little or no hook.[2]

Each group contains a number of subspecies. "Sumichrast's scrub jay" stands apart from the others in its altruistic breeding behavior. Its remaining races are generally not quite as pale but have washed-out colors with indistinctly marked borders. Certainly, some gene flow among these populations occurs, but while the hybrid zone between the californica and woodhouseii groups is very limited.[2][11]

The subspecies are:[2]

California scrub jay, Aphelocoma (californica) californica

"California" scrub jay (Aphelocoma californica immanis), showing the well-marked breast band of the coastal races. Acorns are a typical food.
Another "California" scrub jay. Note bright white plume breaking the breast band. Prominent markings in eye region are typical of male birds.
"California" scrub jay
"California" scrub jay in flight in Ben Lomond, Santa Cruz County, California
From Puget Sound through the Willamette Valley to Douglas County, Oregon
A large subspecies. Somewhat duller and lighter in color than californica due to gene flow from inland populations. Blue of head and neck less purplish than in woodhouseii group. Back usually quite brownish, underside and especially breast quite whitish, undertail coverts usually tinged pale blue or gray in males. Bill strong, wings and tail fairly short.
Coastal SW Oregon from Rogue River valley south to Napa and Sonoma Counties; eastern limit the inner California Coast Ranges.
Similar to californica, but head and back more intensely colored, with bright purplish tinge to blue of head. Color similar to nominate, thus darker than immanis and most oocleptica. Relative to nominate californica, blue areas more purplish and brighter, breast darker than rest of underside.
From Jackson, Klamath, and Lake Counties, Oregon, through Sacramento and San Joaquin Valleys and surrounding mountains to Kern County, San Francisco Bay area, and Alpine County. Eastwards to Inyo County and Virginia Mountains (Washoe County, Nevada), where it intergrades with nevadae of the woodhouseii group.
Quite variable according to the extent of gene flow between this taxon and nevadae. Generally similar to californica but larger; color of head and neck varies in lightness and amount of purplish hue. Back grayish; undertail coverts usually white. Bill usually heavy but variable according to habitat type (less heavy in birds of pinyon woodland).
California Coast Ranges from San Mateo County and SE Alameda County to SW Ventura County.
Blue of head usually strongly tinged purple. Back bluish-brownish gray, bluer towards the rump. Incomplete bluish-violet breast band. Underside greyish white, darker on the breast. Undertail coverts white tinged with blue. Thighs gray. Rectrices and remiges dark blue, the larger feathers duller. Bill heavy, tip strongly hooked.
Coastal SW California, east to Little San Bernardino Mountains, some isolated mountain ranges in W Mojave Desert, and Whale Peak (San Diego County). Southwards through N Baja California, Mexico (Sierra de Juárez, Sierra San Pedro Mártir) to Todos Santos Bay
Smaller and darker than californica, with more intense purplish and brown coloration on head and back, respectively; prominent gray streaking on throat and distinct breast collar. Belly with smoky gray wash, lighter in the middle. Generally more intense coloration overall. Bill heavy.
Only occurs in Single-leaf Pinyon woods on Eagle Mountain, Joshua Tree National Park.
Smaller, lighter and grayer than californica. Bill not as heavy. Apparently an isolate of hybrid origin between A. c. obscura and nevadae of the woodhouseii group.

Woodhouse's scrub jay, Aphelocoma (californica) woodhouseii

A western scrub jay of the "Woodhouse's" population, from New Mexico
Great Basin from N Nevada southwards, some isolated mountain ranges in Death Valley and Mojave Desert from E California to the SW of New Mexico, south to NE Sonora and extreme NW Chihuahua. Some hybridization with A. c. oocleptica (californica group) at the north-western edge of its range.
Lighter and duller than woodhouseii; light blue undertail coverts. Bill longish, quite pointed, and tapering, not hooked at tip.
Rocky Mountains foothills, from N Utah/S Wyoming south through NW Chihuahua and W Texas, sometimes ranging farther into that state.
Blue of neck with dull grayish hue; back grayish brown. Undertail coverts blue. Bill heavy but straight, hardly hooked at tip.
Hitherto only known from Edwards Plateau (Texas); area and extent of possible contact with woodhouseii undetermined. Possibly this subspecies at Caprock Escarpment, where species settled in the 1950s.
Darker than woodhouseii with hint of breast collar. Lower breast with brownish hue, large white patch on lower belly. Undertail coverts white; in adult males usually with some blue feather tips. Back quite brown. Young birds conspicuously paler than in woodhouseii. Heavy, fairly blunt bill.
Sierra Madre Occidental, primarily in Chihuahua; intergrading with nevadae at NW of range.
Lighter and larger than woodhouseii, with a hint of a blue collar. Undertail coverts white. Long wings and fairly short, heavy bill.
Lower Sierra Madre Oriental, Mexico, from S Coahuila to Tlaxcala; generally separated from texana woodhouseii; range adjacent to grisea in S Chihuahuan Desert. Apparently replaced by Mexican jay at higher-altitude woodland towards S of range.
Larger and duller than woodhouseii. Back brown with blue tinge, sometimes quite bluish. Supercilium faint and small. Underside qhite light; lower belly white. Undertail coverts dull white. Bill and wings as in grisea, young birds browner than texana.

The name of this subspecies commemorates the American explorer and collector Samuel Washington Woodhouse.

Sumichrast's scrub jay, Aphelocoma (californica) sumichrasti

From Distrito Federal southeastwards through Veracruz, Puebla, and Oaxaca.
Bright blue head color, with blackish ear patches. Faint white supercilium. Back grayish-brown, blue towards the tail. Light gray streaks on throat; traces of a faint grayish or grayish-blue breast collar. Thighs smoky gray. Remiges and rectrices dark dull blue. Large, with very long wings. Heavy, slightly hooked bill.
SW Oaxaca and central Guerrero. Apparently separated from sumichrasti by Rio Balsas valley.
Duller and lighter than sumichrasti. Largest of all western scrub jays.

The common name of this subspecies commemorates the Mexican naturalist Francis Sumichrast.[12]

Footnotes

A Etymology: Aphelocoma, 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. californica, Latin: "from California".

References

  1. ↑ BirdLife International (2012). "Aphelocoma californica". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. 1 2 3 4 5 Curry, Robert L.; Peterson, A. Townsend & Langen, T.A. (2002): Western Scrub Jay (Aphelocoma californica). In: Poole, A. & Gill, F. (eds.): The Birds of North America 712. Academy of Natural Sciences, Philadelphia, PA & American Ornithologists' Union, Washington, D.C. Online version, retrieved February 25, 2007. doi:10.2173/bna.712
  3. ↑ Clayton, N. S., Bussey, T. J. & Dickinson, A. (2003). "Can animals recall the past and plan for the future?" (PDF). Nature reviews. Neuroscience 4 (8): 685–91. doi:10.1038/nrn1180. PMID 12894243.
  4. ↑ Raby, C. R.; D. M. Alexis; A. Dickinson; N. S. Clayton (22 February 2007). "Planning for the future by western scrub-jays". Nature 445 (7130): 919–921. doi:10.1038/nature05575. PMID 17314979.
  5. ↑ Clayton, N. S., Dally, J. M. & Emery, N. J. (2007). "Social cognition by food-caching corvids. The western scrub-jay as a natural psychologist". Philosophical transactions of the Royal Society of London. Series B, Biological sciences 362 (1480): 507–22. doi:10.1098/rstb.2006.1992. PMC 2346514. PMID 17309867.
  6. ↑ Dally, J. M., Emery, N. J. & Clayton, N. S. (2006). "Food-caching western scrub-jays keep track of who was watching when". Science 312 (5780): 1662–5. doi:10.1126/science.1126539. PMID 16709747.
  7. ↑ Correia, SP; Dickinson, A; Clayton, NS (2007). "Western scrub-jays anticipate future needs independently of their current motivational state" (PDF). Current Biology 17 (10): 856–61. doi:10.1016/j.cub.2007.03.063. PMID 17462894.
  8. ↑ Clayton, Nicola; Emery, Nathan and Dickinson, Anthony (2006). "The rationality of animal memory: Complex caching strategies of western scrub jays". In Hurley, Susan and Nudds, Matthew. Rational Animals? (PDF). Oxford University Press. pp. 197–216. ISBN 0198528264.
  9. ↑ Scrub jays react to their dead, bird study shows: 'Funerals' can last for up to half an hour. Sciencedaily.com (2012-09-11). Retrieved on 2013-03-22.
  10. ↑ Emslie, Steven D. (1996). "A fossil scrub-jay supports a recent systematic decision" (PDF). Condor 98 (4): 675–680. doi:10.2307/1369850.
  11. 1 2 3 4 Rice, Nathan H.; Martínez-Meyer, Enrique & Peterson, A. Townsend (2003). "Ecological niche differentiation in the Aphelocoma jays: a phylogenetic perspective" (PDF). Biological Journal of the Linnean Society 80 (3): 369–383. doi:10.1046/j.1095-8312.2003.00242.x.
  12. ↑ Beolens, Bo; Watkins, Michael (2003). Whose Bird? Men and Women Commemorated in the Common Names of Birds. London: Christopher Helm. p. 329.

Further reading

External links

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