北美星鸦种

进食习性

北美星鸦通常埋葬种子的方式贮藏食物。

体重

北美星鸦的平均体重约为130.0克。

栖息地

栖息地包括温带森林、城市、亚热带或热带的旱林和高海拔疏灌丛。

保护级别

该物种的保护状况被评为未濒危。

Clark's nutcracker (Nucifraga columbiana), also known as Clark's crow, is a passerine bird in the family Corvidae, native to the mountains of western North America. The nutcracker is an omnivore, but subsists mainly on pine nuts, burying seeds in the ground in the late summer and fall, and then retrieving them in the winter and spring by memory. The bird was described by the Lewis and Clark Expedition, with William Clark first observing it in 1805 along the banks of the Salmon River, a tributary of the Columbia River.

Etymology and history

In William Clark's initial description of the bird, he mistakenly described it as a woodpecker, writing "I saw today [a] bird of the woodpecker kind, which fed on pine burrs. Its bill and tail white; the wings black; every other part of a light brown, and about the size of a robin."

Clark's nutcracker's scientific name literally means "nutcracker of the Columbia". In 1806, Meriwether Lewis recorded a more detailed description from specimens collected along the Clearwater River in Idaho.

Taxonomy

Originally placed in the genus Corvus by Wilson, by 1840 Clark's nutcracker was included in Nucifraga by John James Audubon. Through the second half of the 19th century, taxonomists placed Clark's nutcracker in its own genus, Picicorvus, as suggested by Charles Lucien Bonaparte. In 1894, ornithologist Robert Ridgway suggested its return to Nucifraga, citing morphological similarities to its modern Eurasian congenerics.

Distribution and habitat

This species is present in western North America from British Columbia and western Alberta in the north to Baja California and central New Mexico in the south. There is also a small isolated population on the peak of Cerro Potosí (elevation 3,700 m (12,100 ft)), in Nuevo León, northeast Mexico. It is mainly found in mountains at altitudes of 900–3,900 m (3,000–12,800 ft) in conifer forest. It is not typically migratory, but does seasonally move between higher elevations in the summer breeding season and lower elevations in the winter.

Description

Nucifraga columbiana is roughly the size of a jay, and slightly smaller than its Eurasian congenerics (northern, southern, and Kashmir nutcrackers). Its head, back, belly, and ventrum are covered in gray feathers, and it sports black wings with white tips on secondary feathers. Its tail feathers are easily distinguishable in flight, with central black feathers bordered by white feathers on either side. It has a long, black, pointed bill whose shape is specialized for removing the scales of pinecones.

Measurements

• Length: 27–30 cm (11–12 in)
• Weight: 106–161 g (3.7–5.7 oz)

Food

The most important food resources for this species are the seeds of pines (Pinus sp.), principally two cold-climate (high-altitude) species of white pine with large seeds: the whitebark pine (P. albicaulis) and limber pine (P. flexilis). Seeds of other high-altitude pine species are also eaten, including the foxtail pine (P. balfouriana), bristlecone pine (P. longaeva) western white pine (P. monticola), and ponderosa pine (P. ponderosa). Douglas fir (Pseudotsuga menziesii) is one of the few non-pine conifers whose seeds Clark's nutcracker regularly eats.

Nesting

The species usually nests in pines or other types of conifers during early spring. Two to six eggs are laid per nest, with incubation occurring over approximately 18 days. Incubation is performed by both the male and female parents, and both the male and the female develop brood patches; however, the female parent contributes significantly more time to incubation than the male. Nestlings fledge between 3–4 weeks after hatch.

Whitebark pine mutualism

Clark's nutcracker is the primary seed disperser for whitebark pine (Pinus albicaulis). Whitebark pine is in decline throughout its range, due to infection by white pine blister rust (Cronartium ribicola), widespread outbreaks of mountain pine beetle, and the long-term effects of fire suppression. Clark's nutcracker is an integral part of the whitebark pine restoration process: Clark's nutcracker must remain in whitebark pine forests and cache the seeds in excess, so that healthy trees will continue to grow.

Vocalization

Corvids, of which Clark's nutcracker is a member, do not typically have songs. However, they produce between eight and thirteen variable calls, generally phonetically described as "kraak" or "kraa". Additional clicking or crackling calls are made, likely used for pair bonding.