The Ferruginous hawk (Buteo regalis)

The Ferruginous (fer-oo-jin-us) hawk is named after the rust (ferrous) coloration on the back and shoulders and legs which are set off by the white underside of the wings, breast and belly.
 

Ferruginous Hawk - Buteo_regalis_-California_-flying-8.jpg: Alan Vernon - 
derivative work: Snowmanradio (talk) - CC BY 2.0

Although its Latin name, Buteo regalis, means Royal hawk it is not a true hawk such as the sparrow hawk. Instead it is one of the broad-tailed hawks also known as buzzards or buteos  and  shares many similarities to the Rough-legged hawk (Buteo lagopus) including feathered legs.

With a length ranging between 20-26 inches and a wingspan of 48-60 inches and weighing  2.2-4.5 pounds it is the heaviest and largest of the Buteos of North America and only the Golden eagle, Bald eagle and  largest of female Snowy owls of the North American raptors are heavier.  Read more