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Western Scrub-jay (Aphelocoma californica) - wiki
| 제목: | Western Scrub-jay (Aphelocoma californica) - wiki
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Western Scrub-jay
From Wikipedia, the free encyclopedia
[Photo] California Scrub-jay, Aphelocoma californica californica. Date: 6 October 2006. By http://en.wikipedia.org/wiki/User:Sirevil (Crop)
The Western Scrub-jay (Aphelocoma californica), also known as California Jay or Long-tailed Jay (and see below) is a species of scrub-jay native to western North America, ranging from southern Washington to central Texas and central Mexico. In recent years, it has expanded its range into the Puget Sound region of Washington. The Santa Cruz or Island Scrub-jay (Aphelocoma insularis), found only on Santa Cruz Island, and the Florida Scrub-jay (Aphelocoma coerulescens), a Floridan endemic, are its closest relatives (Curry et al. 2002). The Western Scrub-jay is nonmigratory and can be found in urban areas, where it can become tame and will come to bird feeders.
This species is 27-31 cm (11.5 in) long (including its tail), and weighs about 80g. 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. Western Scrub-jays feed on small animals, eggs and young of other birds, insects, and (particularly in winter) nuts and berries. True to their name, Western Scrub-jays inhabit areas of low scrub, preferring pinyon-juniper forests, oak woods and sometimes mesquite bosques. They are known for hoarding and burying brightly colored objects.
Nests are built low in trees or bushes, 1m to 10m above the ground, primarily by the female while the male guards her efforts. The nests are sturdy, with an outside diameter of 33cm to 58cm, 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 background with irregular, olive-colored spots or markings, and pale grayish-white to green background with reddish-brown spots. The female incubates the eggs for about 16 days. The young leave the nest about 18 days after hatching.
The Western Scrub-jay is one of the species whose populations are being adversely affected by the West Nile Virus, particularly in California's Central Valley.
Systematics
The Western, Santa Cruz, and Florida Scrub-jays were once considered subspecies of a single species termed the "Scrub Jay". However, they are now known to be well distinct (Emslie 1996, Curry et al. 2002, Rice et al. 2003). 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 as if there are 2 clades, namely a Pacific one west and another one east of the Rocky Mountains; the relationships of populations in the latter are not resolvable to satisfaction though (Rice et al. 2003). Thus, it is fairly likely that 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 too. Paleogeography of the Rocky Mountains range supports this scenario.
Inland birds (Woodhouse's Scrub-jay, woodhouseii group) differ in plumage (paler blue above, and with an indistinct and usually incomplete breast band) from the coastal birds (California Scrub-jay, californica group; darker blue above, and with a strongly defined - but not necessarily complete - blue breast band). They also differ in ecology and behavior; the beaks of the Pacific group are usually strong and hooked at the tip as they feed on acorns, whereas the pinyon-nut feeding inland group has a longer, slimmer and straighter bill with little or no hook (Curry et al. 2002).
Each group contains a number of subspecies. In the woodhouseii group, the quite pale but distinctly patterned southernmost subspecies sumichrasti and remota ("Sumichrast's Scrub-jay") stand apart; its remaining races are generally not quite as pale but have washed-out colors with indistincly marked borders. Although these were considered to constitute well-marked groups, the molecular data of Rice et al. (2003) was unable to distinguish woodhouseii and sumichrasti. Thus, these differences seem to reflect patterns independent of phylogeny such as adaptations to local conditions, or perhaps character displacement with the Mexican Jay which is more similar to the northern inland than to the southernmost taxa; its range overlaps with the latter but not the former. Certainly, some gene flow between these populations occurs, but while the hybrid zone between the californica and woodhouseii groups is very limited, the geographically isolated southern populations seem genetically far less distinct (Curry et al. 2002, Rice et al. 2003).
Following Curry et al. (2002), the subspecies are:
California Scrub-jay, Aphelocoma (californica) californica
Aphelocoma californica immanis Grinnell, 1901 - Interior Scrub-jay
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.
Aphelocoma californica caurina Pitelka, 1951
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.
Aphelocoma californica oocleptica Swarth, 1918 - Nicasio Scrub-jay. Includes A. c. superciliosa
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).
Aphelocoma californica californica (Vigors, 1839)
California Coast Ranges from San Mateo County and SE Alameda County to SW Ventura County.
Blue of head usually strongly tinged purple. Bach 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.
Aphelocoma californica obscura Anthony, 1889 - Belding's Scrub-jay
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 Ju??rez, Sierra San Pedro M??rtir) 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.
Aphelocoma californica cana Pitelka, 1951 - Eagle Mountain Scrub-jay
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.
Aphelocoma californica hypoleuca Ridgway, 1887 - Xantus' Scrub-jay. Includes A. c. cactophila
Arid regions of central and southern Baja California south of a line through Bah??a Magdalena, Sierra de Calamaju??, and Loreto, Baja California Sur
Smaller and somewhat lighter than californica with less purplish hue to blue of head. Underside, including blue on breast, very light. Some have blue or gray tinge to undertail coverts. Bill proportionally longest in californica group.
Woodhouse's Scrub-jay, Aphelocoma (californica) woodhouseii
Aphelocoma californica/woodhouseii nevadae Pitelka, 1945a - Nevada Scrub-jay
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.
Aphelocoma californica/woodhouseii woodhouseii (Baird, 1858)
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.
Aphelocoma californica/woodhouseii texana Ridgway, 1902 - Texas Scrub-jay
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.
Aphelocoma californica/woodhouseii grisea Nelson, 1899
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.
Aphelocoma californica/woodhouseii cyanotis Ridgway, 1887 - Blue-eared Scrub-jay
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.
Aphelocoma californica/woodhouseii sumichrasti (Baird and Ridgway, 1874) - Sumichrast's Scrub-jay
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.
Aphelocoma californica/woodhouseii remota Griscom, 1934 - Chilpancingo Scrub-jay
SW Oaxaca and central Guerrero. Apparently separated from sumichrasti by Rio Balsas valley.
Duller and lighter than sumichrasti. Largest of all Western Scrub-jays.
http://en.wikipedia.org/wiki/Western_Scrub-jay
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