Quaglia della Virginia

Identificazione

C. virginianus is a moderately-sized quail, and is the only small galliform native to eastern North America. The bobwhite can range from 24 to 28 cm (9.4 to 11.0 in) in length with a 33 to 38 cm (13 to 15 in) wingspan. As indicated by body mass, weights increase in birds found further north, as corresponds to Bergmann's rule. In Mexico, northern bobwhites weigh from 129 to 159 g (4.6 to 5.6 oz) whereas in the north they average 170 to 173 g (6.0 to 6.1 oz) and large males can attain as much as 255 g (9.0 oz). Among standard measurements, the wing chord is 9.7 to 11.7 cm (3.8 to 4.6 in), the tail is 5 to 6.8 cm (2.0 to 2.7 in) the culmen is 1.3 to 1.6 cm (0.51 to 0.63 in) and the tarsus is 2.7 to 3.3 cm (1.1 to 1.3 in). It has the typical chunky, rounded shape of a quail. The bill is short, curved and brown-black in color. This species is sexually dimorphic. Males have a white throat and brow stripe bordered by black. The overall rufous plumage has gray mottling on the wings, white scalloped stripes on the flanks, and black scallops on the whitish underparts. The tail is gray. Females are similar but are duller overall and have a buff throat and brow without the black border. Both sexes have pale legs and feet.[citation needed]

Tassonomia

There are 20 recognized subspecies in four groups. One subspecies, the Key West bobwhite (C. v. insulanus), is extinct. The subspecies are listed in taxonomic order:<p>The holotype specimen of Ortyx pectoralis Gould (Proc. Zool. Soc. London, 1842 (1843), p.182.) is held in the collections of the National Museums Liverpool at the World Museum, with accession number D3713. The specimen died in the aviary at Knowsley Hall, Lancashire and came to the Liverpool national collection via the 13th Earl of Derby's collection, which was bequeathed to the people of Liverpool in 1851.

Nome scientifico

Colinus virginianus

Autorità

(Linnaeus, 1758)

Ordine

Galliformi

Famiglia

Odontophoridae

Genere

Colinus

Areale e habitat

The northern bobwhite can be found year-round in agricultural fields, grassland, open woodland areas, roadsides and wood edges. Its range covers the southeastern quadrant of the United States from the Great Lakes and southern Minnesota east to New York State and southern Massachusetts, and extending west to southern Nebraska, Kansas, Oklahoma, Colorado front-range foothills to 7,000 feet, and all but westernmost Texas.<p>It is absent from the southern tip of Florida (where the extinct Key West bobwhite subspecies once lived) and the highest elevations of the Appalachian Mountains, but occurs in eastern Mexico and in Cuba, and has been introduced to Hispaniola (both the Dominican Republic and Haiti), the Bahamas, the Turks and Caicos Islands, the U.S. Virgin Islands (formerly), Puerto Rico, France, China, Portugal, and Italy. Isolated populations also have been introduced in Oregon and Washington. The northern bobwhite has also been introduced to New Zealand.<p>There is no self-sustaining population in Pennsylvania, where the bird is considered extirpated; it is also considered extirpated in the states of New Hampshire and Connecticut. Its distribution in New York has been limited to Suffolk and Nassau Counties on Long Island, as well as potential population pockets in Upstate New York. The bird is considered declining or extirpated throughout much of the Northeastern United States. Similarly, the bird is almost extirpated from Ontario (and Canada as a whole), with the only self-sustaining population confirmed to exist recorded on Walpole Island.

Migrazione

Resident species

Comportamento

Like most game birds, the northern bobwhite is shy and elusive. When threatened, it will crouch and freeze, relying on camouflage to stay undetected, but will flush into low flight if closely disturbed. It is generally solitary or paired early in the year, but family groups are common in the late summer and winter roosts may have two dozen or more birds in a single covey.<p>The species was once considered monogamous, but with the advent of radio telemetry, the sexual behavior of bobwhites has better been described as ambisexual polygamy. Either parent may incubate a clutch for 23 days, and the precocial young leave the nest shortly after hatching. The main source of nest failure is predation, with nest success averaging 28% across their range. However, the nest success of stable populations is typically much higher than this average, and the aforementioned estimate includes values for declining populations.<p>Brooding behavior varies in that amalgamation (kidnapping, adopting, creching, gang brooding) may occur. An incubating parent may alternatively stay with its young. A hen may re-nest up to four times until she has a successful nest. However, it is extremely rare for bobwhites to hatch more than two successful nests within one nesting season.<p>The northern bobwhite's diet consists of plant material and small invertebrates, such as snails, ticks, grasshoppers, beetles, spiders, crickets, and leafhoppers. Plant sources include seeds, wild berries, partridge peas, and cultivated grains. It forages on the ground in open areas with some spots of taller vegetation.<p>Optimal nutrient requirements for bobwhite vary depending on the age of bird and the time of the year. For example, the optimal protein requirement for egg laying hens (23% protein) is much higher than for males (16%).

Conservazione

Tendenza della popolazione

declining