Both sexes have dark brown back and wings, light mottled-brown head, and a white tail with a black terminal band. Most birds have a wide, dark brown belly band. In flight, the wing undersides are white with brown tips. Light-phase birds have a dark patch of brown midway along the forward edge of the wing. Dark-phase birds are dark chocolate-brown all over, except for white wing feathers on the undersides, and the mostly white tail. The sexes can be told apart by the tail: Males have dark barring above the terminal band, while females have a single solid terminal band, with no barring. Rough-legged Hawks range in length from 19 to 24 inches, and have a wingspan of 48 to 56 inches.
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.
Other Montana buteo hawks lack the white tail with dark terminal band. The time of year is the best clue, since Rough-legged Hawks are the most common hawk seen during the winter, but are absent from Montana during the summer when other hawks are most common. Immature Golden Eagles are larger and have dark flight feathers.
Western Hemisphere Range
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Rough-legged Hawks nest in northern Canada and Alaska, and migrate to the lower 48 states in winter. They are most numerous in Montana from October through March. In winter, Rough-legged Hawks are the most common buteo hawk. Bozeman area migration: November 5 to December 10 and March 20 to April 8 (Skaar 1969).
Rough-legged Hawks hunt over grasslands and agricultural land. They are often seen perched on utility poles and fence posts. Found in open areas of the Gallatin Valley (Skaar 1969).
They primarily prey upon small mammals such as ground squirrels, rabbits, and mice. They occasionally eat birds and insects.
Light phase birds are most frequent in Bozeman area, but dark birds are regularly seen (Skaar 1969).