Hi,
Interesting bird. Are there any more photos available?
If the lengths of the primaries are portrayed accurately, then the third
longest (instead of fourth) would make it a dark morph juv. Swainson's Hawk.
This is the only western buteo with that feature.
The head shape is not typical of a Ferruginous Hawk and I am not able to
see the gape extension (under the eye) in this photo. Tail barring is not
right either. Check out the cover on Wheeler's new book.
And as had been pointed out earlier, there is no dark patagium, so
unlikely to be a RTHA.

Bud Anderson
Falcon Research Group
Box 248
Bow, WA. 98232
360.757.1911