The Raptors of Arizona. University of Arizona Press. The subspecific epithet for the race occurring in Arizona, cactorum , alludes to cactus, a vegetation with which it frequently associates in the northern portion of its range. The term ferruginous refers to the rusty red tail and upper side of the outer vanes of the flight feathers.
Females average slightly larger than males.
The back and upper wing coverts are plain light brown, with occasional conspicuous white spots on the upper wing coverts and small, regularly spaced whitish spots on the outer primaries. Both the tail and the flight feathers are duskily barred, the dusky and light bars of the tail evenly spaced. The face has a white V and disk. The tarsi are feathered. The eyes are yellow.