In the first photo, two things are of note; the bird's mostly white tail, and the typical long and broad wings of a buteo. That combo might make one think of a Rough-legged Hawk or even a Ferruginous Hawk, but Ferrugies have more pointed wingtips, and Roughies have more uniformly wide wings. Red-tailed Hawks have exactly the same wing shape as our mystery bird; long like a buteo, but noticeably wider at the base than in those two other species and expanding even more towards the middle of the wing, giving it a look that is more accipiter-like (in a buteo kind of way) than our other two candidates. But what about that tail pattern? The combo of these two features fits for a Harlan's Hawk, a subspecies of Red-tailed Hawk

Additional marks on the bird can be seen in this second photo, where the dark head is visible, along with the heavily streaked but white upper breast. From below, the tail is still showing some white, all of which are key field marks for Harlan's. Lastly, the underwing pattern of a dark-trailing edge matches that of an adult Red-tail/Harlan's; an immature bird would not have the dark trailing edge.

Photographed on Road R, northeast of Willows, California, on 12-4-15.