Rough-legged Hawk

Rough-legged Hawk

Rough-legged Hawk

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Common Name: Rough-legged Hawk
Also referred to as: American Roughleg, Rough-legged Buzzard
Genus species: Buteo lagopus
Recognized subspecies: Buteo lagopus sanctijohannis (Gmelin)
Family: Accipitridae
Order: Falconiformes



General Description:

  • Total length: 47 to 59 cm.
  • Wing chord: 372 to 438 mm.
  • Tail: 210 to 235 mm.
  • Weight: 715 to 1400 grams.
  • Sexes dimorphic with the female being slightly larger.
  • Legs feathered to base of the feet.
  • Plumage is variable, with both a light morph and a dark morph. The light morph is more common.
  • Abdomen of male barred, rather than blotched with brown as in the female.
  • The rump and base of tail are white, with dark coloration closer to the tip of the tail.
  • Bands on tail of male are narrow, whereas the female has one or more broad bands on the tail.
  • Head, neck and upper breast of light morph are light brown. The breast typically has dark streaking.
  • Dark morph birds, more common in eastern portions of North America, appear to be nearly black throughout, except for a white patch on the nape.
  • Black “wrist patch” on the underside of the wing is present in both the light and dark morph.

 

North American Distribution
Habitat Description
Movements and Migratory Habits
Diet and Foraging Strategy
Reproduction
Conservation Status

 

North American Distribution:

  • Breeds from western and northern Alaska, northern Yukon, throughout the arctic islands in Canada’s far north, northern Labrador, south to northern Northwest Territories, southeast Nunavut, northern Manitoba, northern Ontario, northern Quebec, and Newfoundland.
  • Winters from southern Canada south to California, southern Arizona, southern New Mexico, southern Texas, Missouri, Kentucky and Maryland. May also occasionally over-winter in the Canadian provinces.
  • The Rough-legged Hawk does not breed in Alberta, but may be found throughout the province during migration. May occasionally over-winter within the province.

Habitat Description:

  • Rough-legged Hawks are found in arctic and subarctic habitats north of the tree line during the breeding season.
  • Habitats are generally restricted to treeless tundra, but areas along the edge of the tree line are also inhabited.
  • Escarpments, rock outcrops, cliff ledges, ravines and steep riverbanks are topographic features commonly used as nesting sites.
  • May also nest in trees. Tree nests most commonly in spruce (Picea spp.); may occasionally nest in cottonwoods (Populus spp.).
  • Breeding densities likely limited by available nesting sites.
  • In winter and during migration, Rough-legged Hawks prefer open, treeless areas such as prairies, shrub-steppes, open fields, bogs, marshes and dunes.
  • Avoid densely forested and settled areas at all times of the year.

Movements and Migratory Habits:

  • The Rough-legged Hawk is a medium distance migrant.
  • Southward migration is primarily from mid to late September, but some individuals may depart from breeding grounds as early as late August.
  • The northward migration from the wintering grounds is generally from mid March to early April, but some may migrate as early as February or as late as mid April.
  • Home ranges within the winter range are generally 10 to 15 square kilometres. Little information is known about home range size in the breeding range.

Diet and Foraging Strategy:

  • Mammals, primarily rodents, are thought to comprise 80% or more of the Rough-legged Hawk’s diet (especially voles and lemmings).
  • Medium sized mammals, such as ground squirrels and rabbits, may also contribute to the diet.
  • Passerine birds and ptarmigans are opportunistically consumed.
  • Winter foods are slightly more variable, but rodents continue to comprise the largest portion of the diet. Prey as large as lagomorphs and pheasants have been reported in the winter range.
  • Hunt in open areas from the air or from an elevated perch.

Reproduction:

  • Rough-legged Hawks are seasonally monogamous. Pair bonds may be retained from one year to the next, but there is insufficient evidence to support this.
  • The nest is a typical raptor nest: a mass of sticks lined with moss and other fine material.
  • Nests are on cliffs, boulders, steep slopes, shelves in steep riverbanks or in trees.
  • Female builds the nest, while the male provides the majority of the material.
  • Nest sites usually have a broad view of the surrounding area.
  • Only one brood produced each breeding season.
  • Clutch size may range from 2 to 7 eggs, but 3 to 5 is common.
  • Eggs are laid in 2-day intervals.
  • There is discrepancy about the incubation period of the Rough-legged Hawk. Some reports indicate an incubation period of 31 days in wild birds, while other reports indicate an incubation period of 37 days.
  • The female incubates. The male will cover the nest while the female feeds.
  • The asynchronous hatch occurs over 2 to 4 days.
  • Hatchlings are semi-altricial.
  • Brooding is done mostly by the female.
  • Fledging occurs at 31 to 40 days of age.

Conservation Status:

  • Federal: Not at Risk
  • Provincial: Secure


ReferencesRough-legged Hawk photo © 2009 Cynthia Lindow. Retrieved from www.istockphoto.com/stock-photo-8414719-rough-legged-hawk.php on 22/09/09. Used with permission.

Alberta Sustainable Resource Development (ASRD). 2008. Search species and status category. <http://www.srd.gov.ab.ca/fishwildlife/speciesatrisk/statusofalbertawildspecies/search.aspx>. Accessed 19 October 2009.

Bechard, M.J. and T.R. Swem. 2002. Rough-legged Hawk (Buteo lagopus), The Birds of North America Online (A. Poole, Ed.). <http://bna.birds.cornell.edu/bna/species/641doi:10.2173/bna.641>. Accessed 19 October 2009.

Godfrey, W.E. 1986. Birds of Canada, revised edition. National Museum of Natural Sciences, Ottawa, Canada.

Government of Canada. Species at risk public registry. 2008. <http://www.sararegistry.gc.ca/sar/index/default_e.cfm>. Accessed 19 October 2009.

Johnsgard, P.A. 1990. Hawks, Eagles & Falcons of North America: biology and natural history. Smithsonian Institution Press, Washington, USA.

Salt, W.R. and J.R. Salt. 1976. The birds of Alberta. Hurtig Publishers, Edmonton, Alberta, Canada.