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Aug 27 2011

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Rough-legged Hawk (Buteo lagopus)


Rough-legged Hawk

[order] ACCIPITRIFORMES | [family] Accipitridae | [latin] Buteo lagopus | [authority] Pontoppidan, 1763 | [UK] Rough-legged Hawk | [FR] Buse pattue | [DE] Rauhfuss-Bussard | [ES] Ratonero Calzado | [NL] Ruigpootbuizerd

Subspecies

Monotypic species

Genus

Members of the genus Buteo are broad-winged, broad-tailed hawks, Well adapted for soaring. The bill, legs and talons are of average proportions. There is much colour variation both within the species, and, by way of phases, within individual species. In all cases the young are quite different from adults in that they are all well camouflaged with an overall brown appearance with varying amounts of striping below and paler mottling above.
The 25 species are spread worldwide with the exception of Australasia and much of the Indian sub-continent.

Physical charateristics

Color pattern like Buzzard (Buteo buteo), but smaller-sized (L 60 cm). Extremely variable. From dark morph through reddish morph to very pale morph. Typical morph shows pale head, breast and tail contrasting with rufous belly, and lacks tail barring of most other buzzards. Dark carpal patches, rusty underwing coverts, flight feathers paler with black trailing edge and wing tip.
Female slightly larger than male. Juvenile has faintly barred tail, black on trailing edge of wing less marked. Race cirtinsis smaller, often paler, lacks dark morph.

Listen to the sound of Rough-legged Hawk

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Copyright remark: Most sounds derived from xeno-canto


wingspan min.: 123 cm wingspan max.: 140 cm
size min.: 49 cm size max.: 59 cm
incubation min.: 30 days incubation max.: 32 days
fledging min.: 34 days fledging max.: 32 days
broods: 1   eggs min.: 3  
      eggs max.: 4  

Range

North America, Eurasia : widespread

Habitat

Rocky or stony country, semi desert and steppe, also open woodland or woods with clearings, from plains and foothills to mountains.
In winter, widely scattered in variety of habitats, from desert to cultivation and wooded areas.
Uses prominent perches on trees, posts, rocks, etc.

Reproduction

Bulky stick nests are built high on cliff ledges or recesses, rocky or dirt outcrops, or on eroded riverbanks with a good view of the surrounding area. Rarely nest on level ground. Where cliffs are not available, trees and occasionally man-made structures will be used. Nests are refurbished each year and can become quite large; alternate nests may be built nearby. Favored sites are likely traditional and used for many years by the same pair unless they are displaced by another raptor. Whenever possible, the highest of all potential nest sites will be chosen.

Rough-legged hawks become sexually mature at 2 years and are monogamous. The pair bond is maintained at least through the breeding season. Replacement clutches are sometimes laid, particularly if the first clutch is lost before hatching. As with most arctic birds of prey, the Rough-legged hawk’s productivity is closely tied to their prey. In years with high prey populations, more eggs are produced and more chicks survive to fledge. In low prey years, the predators may not breed.
Eggs rounded oval, not glossy; white, streaked and blotched reddish-brown, occasionally only slightly, very rarely not at all. Clutch: 3-4 (2-7). Varies with food supply, particularly lemmings and voles, with 2-3 in poor years and 5-7 in good years.

Feeding habits

Essentially a hunter of small mammals, particularly rodents, voles, mice, rats, gerbils, rabbits and pikas.
Sometimes reptiles, lizards and snakes, some small birds, amphibians and large insects.
Rather sluggish open waits for long periods on perch or on ground and also forages with soaring flight, hangs on wind, without beating wings, to survey ground.
Can take advantage of fires to prey escaping animals.

Video Rough-legged Hawk

copyright: thunefeld


Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The rough-legged hawk is a diurnal (daytime), and sometimes crepuscular (dusk and dawn), hunter that pursues prey from elevated perches or the air depending on availability of perches, weather, and possibly other factors. When hunting from the air, soars or uses flapping/gliding flight but periodically kites into the wind. Normally catches live prey on the ground, attacking from above in vertical or diagonal pounces. It does not pursue prey by walking, running, or hopping on ground. These hawks also rob prey from other birds. After capture, prey is carried to a nearby perch for ingestion.

These hawks are complete migrants with the entire population moving from breeding grounds in the arctic/subarctic to open country in southern Canada and U.S. Usually migrate alone or in loosely aggregated flocks. When migrating, use powered flight and flapping and gliding intermittently, or soar on updrafts and thermals. During migration they are seen primarily in valleys, away from densely forested areas. Undertakes long water crossings (up to 62 miles) by either soaring in circles high out over water or using flapping and sailing flight.

In level flight, The rough-legged hawk tends to utilize steady wing beats with less of the “pump and glide” type of flight that other buteos use. They soar and glide with their wings held in a dihedral or “V”. This species seems less dependent upon the use of thermals than other buteos. In soar, wings and tail spread to full extent. The rough-legged hawk is quite trusting and docile around humans, allowing close approach which can put them at some risk. Around the nest however, it is a fierce defender. Communal roosting at night, on some wintering ranges, has been documented in association with high rodent populations.

In its breeding range it is a bird of open tundra’s and mountainsides, avoiding forests unless they contain plenty of open ground. It soars and hovers over such country with great grace and ease, constantly making use of wind currents, and sometimes quartering the ground, flying low like a harrier. When soaring against the wind it hovers, more than most other buzzards. It perches on rocks, trees, telegraph poles and the like, and when no such perches are available it will sit on a low hummock, boulder or bush. When perched it is normally very erect in posture.
The Rough-legged Buzzard is generally a tame species, allowing close approach by man, but near the nest it is aggressive and excitable. The female is generally more aggressive than the male.
Rough-legged Hawk status Least Concern

Migration

Migratory, with breeding range and winter quarters usually quite separate. Date, duration and distance of migration can vary with southward extent of snow cover and abundance of rodents in breeding range
During migration, it often travels in large flocks. Up to 1,000 a day have been seen passing along the shore of Lake Superior. Mated pairs may remain together in winter, even in flocks. The southward migration from the breeding grounds begins in late August or early September, depending on snowfall, and reaches a peak in temperate latitudes in mid- and late October. The birds settle in their wintering grounds from November to March. The spring migration also depends largely on snow conditions, and in the north-eastern United States and in Russia takes place in late March and early April. Depending on the snow-melt, they arrive in breeding grounds from late April to May, the main northward flight occurring in the second half of April.
In the winter range single Rough-legged Buzzards often adopt a definite territory, which they frequent constantly for several weeks. This territory may be four to six square miles in extent, or more. They show a definite preference for marshy areas near water and tend to concentrate in areas where rodent prey is most abundant, so that the numbers of wintering buzzards may be locally determined by fluctuations in the rodent population. In winter range they will also concentrate in numbers in a small area for a time, roosting gregariously. Although migrant, wounded captive birds can survive a northern winter outdoors.

Distribution map

Rough-legged Hawk distribution range map

Literature

Title Visceral Gout in a Rough Legged Hawk (Buteo lagopus)
Author(s): Robert D. Mumane and Mich l M. Garner,
Abstract: Visceral gout is reported for the first time in a ..[more]..
Source: Journal of Wildlife Diseases, 23(3), 1987, pp. 515-517

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