The Collaborative International Dictionary of English v.0.48:
Roughleg \Rough"leg`\, n. (Zool.)
Any one of several species of large hawks of the genus
Archibuteo, having the legs feathered to the toes. Called
also rough-legged hawk, and rough-legged buzzard.
Note: The best known species is Archibuteo lagopus of
Northern Europe, with its darker American variety
(Sancti-johannis). The latter is often nearly or
quite black. The ferruginous roughleg (Archibuteo
ferrugineus) inhabits Western North America.