Faucon gerfaut

Identification

The gyrfalcon is the largest falcon in the world, being about the same size as the largest buteos (buzzards) but probably slightly heavier. Males are 48 to 61 centimetres (19 to 24 inches) long, weigh .mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}805 to 1,350 grams (1 pound 12+1⁄2 ounces to 2 pounds 15+1⁄2 ounces), with average weights reported as 1,130 or 1,170 g (2 lb 8 oz or 2 lb 9+1⁄2 oz) and have a wingspan from 110 to 130 cm (43 to 51 in). Females are bulkier and larger, at 51 to 65 cm (20 to 25+1⁄2 in) long, 124 to 160 cm (49 to 63 in) wingspan, and of 1,180 to 2,100 g (2 lb 9+1⁄2 oz to 4 lb 10 oz) weight, with average weights of 1,585 or 1,752 g (3 lb 8 oz or 3 lb 13+3⁄4 oz). An outsized female from eastern Siberia was found to have scaled 2,600 g (5 lb 12 oz). Among standard measurements, the wing chord is 34.5 to 41 cm (13.6 to 16.1 in), the tail is 19.5 to 29 cm (7.7 to 11.4 in), the culmen is 2 to 2.8 cm (3⁄4 to 1+1⁄8 in) and the tarsus is 4.9 to 7.5 cm (1+7⁄8 to 3 in). The gyrfalcon is larger, broader-winged and longer-tailed than the peregrine falcon, which it is known to compete with (and occasionally hunt). It differs from the buzzard in general structure, having pointed wings.<p>The gyrfalcon is a very polymorphic species, so its plumage varies greatly. The archetypal morphs are called "white", "silver", "brown", and "black", though they can be coloured on a spectrum from all-white to very dark. The brown form of the gyrfalcon is distinguished from the peregrine by the cream streaking on the nape and crown and by the absence of a well-defined malar stripe and cap. The black morph has a strongly black-spotted underside, rather than finely barred as in the peregrine. White form gyrfalcons are the only predominantly white falcons. Silver gyrfalcons resemble a light grey lanner falcon of larger size. The species shows no sex-based colour differences; juveniles are darker and browner than adults.<p>The black color seems to be sex-linked and to occur mostly in females; it proved difficult for breeders to get males darker than the dark side of slate grey. A color variety that arose in captive breeding is "black chick".

Taxonomie

The gyrfalcon was formally described by Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under its current binomial name Falco rusticolus. The genus name is the Late Latin term for a falcon, Falco, from falx a sickle, referencing the talons of the bird. The species name is from the Latin rusticolus, a countryside-dweller, from rus, "country" and colere, "to dwell". The bird's common name comes from French gerfaucon; in Medieval Latin, it is gyrofalco. The first part of the word may come from Old High German gîr (cf. modern German Geier; ultimately from Proto-Germanic *girį̄ ("greed")) for "vulture", referring to its size in comparison with other falcons; or from the Latin gȳrus for "circle" or "curved path", in turn from the Ancient Greek γῦρος, gûros, meaning "circle" – from the species' circling as it searches for prey, distinct from the hunting of other falcons in its range. The male gyrfalcon is called a gyrkin in falconry.

Nom scientifique

Falco rusticolus

Autorité

Linnaeus, 1758

Ordre

Falconiformes

Famille

Falconidés

Genre

Falco

Répartition et habitat

Migration

Complete migrants

Comportement

The gyrfalcon was originally thought to be a bird of tundra and mountains only; however, in June 2011, it was revealed to spend considerable periods during the winter on sea ice far from land. It feeds only on birds and mammals, the latter of which it takes more regularly than many other Falco species. Like other hierofalcons, it usually hunts in a horizontal pursuit, rather than with the peregrine's speedy stoop from a height. Most prey is killed on the ground, whether they are captured there, or if the victim is a flying bird, forced to the ground. The diet is to some extent opportunistic, but a majority breed and hunt coinciding with ptarmigan and seabird colonies. Avian prey can range in size from redpolls around 20 g (0.71 oz) to geese and capercaillies up to 4 kg (8.8 lb) in weight, but ptarmigans (Lagopus mutus) and Willow Grouses (L. lagopus) are often chief prey in the tundra. Seabirds such as auks, gulls and seaducks may predominate in coastal areas, and waders and ducks such as mallards (Anas platyrhynchos) on wetlands. Other avian prey include corvids, smaller passerines, doves, and other birds of preys.<p>Mammalian prey can be locally important, mainly Arctic ground squirrels (Spermophilus parryii) and Arctic hares (Lepus arcticus), and occasionally Norway lemming (Lemmus lemmus) in peak years. Due to the limit of load that they can carry, gyrfalcons mainly take young hares, but both male and female falcons can take down adult hares up 4.5 kg (9.9 lb) in weight and bring dismembered pieces to their nest. Other mammalian prey can include water voles, muskrats, stoats, minks, Arctic fox pups, and rarely also bats. Prey other than birds and mammals are extremely rare, but brown trout (Salmo trutta) have been recorded as prey.<p>In the early 2000s, it was observed that as possible climate change began to temper the Arctic summers, peregrine falcons were expanding their range north to parts of Greenland, and competing with gyrfalcons. Although it is specially adapted for high-Arctic life, and larger than the peregrine, the gyrfalcon is less aggressive and more conflict-averse, and so is less able to compete with peregrines, which can attack and overwhelm the gyrs. However, it remains on the IUCN's Red List with a Conservation Status of Least Concern.

Conservation

Tendance de la population

stable