Pinyon Jay

识别特征

The pinyon jay is a bluish-grey coloured bird with deeper head colouring and whitish throat with black bill, legs and feet. Roughly intermediate between the blue jay and the Eurasian jay in size, its overall proportions are similar to Clark's nutcracker (Nucifraga columbiana) and this can be seen as convergent evolution, as both birds fill similar ecological niches.

分类信息

The pinyon jay was first collected, recorded, and first described as a species from a specimen shot along the Maria River in what is now northern Montana during the Prince Maximilian of Wied-Neuwied expedition to the interior of North America in 1833. A historical marker at LaHood Park on the Jefferson river in Montana, however, claims that the first pinyon jay known to science was seen and described by the Lewis and Clark Expedition at their campsite on this site on August 1, 1805.<p>It is the sole member of the genus Gymnorhinus. No subspecies are recognised.<p>Genetic analysis suggests that the pinyon jay is an offshoot from a lineage that gave rise to the scrub-jays and relatives (Aphelocoma) and Cyanocitta (the blue jay and Steller's jay).<p>The International Ornithologists' Union has designated "pinyon jay" the official common name for the species. It was historically known as the blue crow or Maximilian's jay.

学名

Gymnorhinus cyanocephalus

命名信息

Wied-Neuwied, M, 1841

目

Passeriformes

科

Corvidae

属

Gymnorhinus

分布与栖息地

Pinyon jays are residents from central Oregon to western South Dakota, south to northern Baja California, northwestern and east-central Arizona, central New Mexico, and western Oklahoma. They winter throughout their breeding range and irregularly from southern Washington to northwestern Montana, and south to Mexico and central Texas. When pinyon seed crops are poor, pinyon jays may wander to central Washington, northwestern Oregon, northern Idaho, northwestern Montana, throughout the Great Basin, Nebraska, Kansas, central-western and southwestern California, southeastern Arizona, central Texas, and northern Chihuahua. The pinyon jay is casual in Iowa and a sight report exists in Saskatchewan.<p>The pinyon jay is a permanent resident of pinyon-juniper (Pinus-Juniperus spp.) woodlands and low-elevation ponderosa pine (Pinus ponderosa) forests in the southwestern United States. Pinyon-juniper woodlands are composed primarily of Colorado pinyon (P. edulis) and Utah juniper (J. osteosperma) and cover vast acreages in Colorado, northern Arizona, Utah, and Nevada. Other pinyon and juniper species occurring in these woodlands include singleleaf pinyon (P. monophylla), Parry pinyon (P. quadrifolia), Mexican pinyon (P. cembroides), alligator juniper (J. deppeana), Rocky Mountain juniper (J. scopulorum), and California juniper (J. californica). The pinyon jay relies on singleleaf pinyon in the northwestern portion of its range and Colorado pinyon in the southeastern portion of its range. Ponderosa pines of the southwestern United States include interior ponderosa pine (P. p. var. scopulorum) and Arizona pine (P. p. var. arizonica). In this article, "pinyon" refers to both Colorado pinyon and singleleaf pinyon, and "ponderosa pine" refers to interior ponderosa pine and Arizona pine unless otherwise specified.<p>Pinyon jays prefer pinyon-juniper woodlands, and ponderosa pine forests. They interact in a mutual relationship with the pinyon. Pinyon trees provide pinyon jays with food, nesting and roosting sites, and breeding stimuli. Pinyon jays influence seed dispersal, establishment, and genetic structure of pinyon populations.<p>Pinyon jays use Colorado pinyon in the southeastern portion of their range and singleleaf pinyon in the northwestern portion of their range. The Colorado pinyon begins to bear cones at 25 years of age and produces "substantial" nut crops at an interval of 4 to 7 years, and sometimes every 3 to 5 years. Good cone crops tend to be localized and occur at irregular and infrequent intervals but are geographically synchronous, perhaps to counteract seed predation. Bumper seed crops of the Colorado pinyon are episodic and are probably linked to favorable climatic conditions.<p>Singleleaf pinyon may not produce cones until 35 years of age with a 2- to the 7-year interval between cone production years. The maximum seed production occurs when trees are 75 to 100 years old.<p>Pinyon-juniper woodlands are characterized as arid, semiarid, or occasionally, dry subhumid. The mean annual temperature varies from 40 to 61 °F (4–16 °C). The climate of ponderosa pine forests in the western United States is arid to semiarid. Weather is an important factor influencing the breeding success and survival of pinyon jays (see sections on mating and survival).<p>The annual mean precipitation in the pinyon-juniper woodlands of the southwestern United States varies widely, depending on elevation, topography, and geography. Precipitation ranges from 10 inches (254 mm) at low elevations to 22 inches (559 mm) at high elevations. Spring and summer are times of drought, and Colorado pinyon and juniper are highly drought resistant. Snow depths are not great, except at higher elevations and northern latitudes, but even then, melting occurs within a few days, especially on south-facing slopes. Ponderosa pine forests in the western United States experienced extreme variations in precipitation, receiving no snow some years and up to 100 inches (2,540 mm) in other years. Heavy spring snowfall in both habitats can create difficult nesting conditions for pinyon jays.<p>Pinyon-juniper woodlands occur on foothills, mesas, plateaus and low mountains from 4,000 to 8,000 feet (1,219–2,438 m) elevation. Ponderosa pine forests in the western United States are most common from 6,000 to 8,500 feet (1,800–2,600). Pinyon jays have been noted foraging with Clark's nutcrackers (Nucifraga columbiana) at elevations up to 11,500 feet (3,505 m) in northern Arizona.<p>Pinyon-juniper woodlands occur in areas with a wide range of soils, with parent materials composed of limestone, lava, and sandstone. Soil textures range from coarse, rocky gravels to fine, compacted clays. Ponderosa pine forests in the western United States occur on igneous and sedimentary parent materials including basalt, volcanic cinder, limestone, and sandstone. Conifer seeds are buried by pinyon jays in areas sparsely covered with vegetation, with patches of bare soil and rocks, indicating well-drained soil.

迁徙

Resident species

行为

Migration pattern: Resident species.

保护状况

Population trend: declining.

种群趋势

declining