|
The pinyon jay (''Gymnorhinus cyanocephalus'') is a jay between the North American blue jay and the Eurasian jay in size. It is the only member of the genus ''Gymnorhinus'', (monotypic). Its overall proportions are very nutcracker-like and indeed this can be seen as convergent evolution as both birds fill similar ecological niches. The pinyon jay is a bluish-grey coloured bird with deeper head colouring and whitish throat with black bill, legs and feet. This species occurs in western North America from central Oregon to northern Baja California and east as far as western Oklahoma though it wanders further afield out of the breeding season. It lives in foothills where the pinyon pines ''Pinus edulis'' and ''Pinus monophylla'' occur. This species is highly social, often forming very large flocks of 250 or more birds, and several birds always seem to act as sentries for the flock, watching out for predators while their companions are feeding. The seed of the pinyon pine is the staple food but they supplement their diet with fruits and berries. Insects of many types are also eaten and sometimes caught with its feet. The nest is always part of a colony but there is never more than one nest in a tree. Sometimes the colony can cover quite extensive areas with a single nest in each tree (usually juniper, live oak or pine). There are usually 3–4 eggs laid, quite early in the season. Incubation is usually 16 days. The male bird normally brings food near to the nest, and the female flies to him to receive it and take back to the nest to feed the chicks that fledge around 3 weeks later. Young are normally fed only by their parents, but once they reach near-fledging size they can sometimes receive a meal from any passing member of the colony, which can continue for some time after leaving the nest. The pinyon jay was first collected, recorded and described as a species from a specimen shot along the Maria River in Northern Montana during the Prince Maximilian of Wied-Neuwied, Expedition to the Interior of North America in 1833. The voice is described as a rhythmic ''krawk-kraw-krawk'' repeated two or three times. ==Distribution== 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.〔American Ornithologists' Union. 2005. (The A.O.U. check-list of North American birds ), 7th edition〕 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.〔 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'').〔Stuever, Mary C.; Hayden, John S. 1996. Plant associations (habitat types) of the forests and woodlands of Arizona and New Mexico. Final report: Contract R3-95-27. Placitas, NM: Seldom Seen Expeditions, Inc.〕 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「pinyon jay」の詳細全文を読む スポンサード リンク
|