What does "roughleg" mean?

Roughleg: 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.