Ferruginous Hawk (Buteo regalis)
In early February 2007, near the same location as described on the main Raptor page, we saw a very similar bird (also power-poling), below:
This might even be the same bird. The grey head and cheeks are characteristic of Ferruginous, as is the mostly white body. When this one flew, we saw very whitish underwings, with black at the tips, but did not see the dark bars that run perpendicular to the front line of the wings toward their outer parts that are visible in the two flight images further above. When the bird turned and we saw its back from behind, it looked brownish, but there was a lozenge of white color on the upper side of the rump.
In November 2007, another (or the same) Ferruginous, now an adult, occupied the same vicinity, below: (Click on each image to enlarge it.)
On December 01 2007, below, we saw apparently the same bird (though framed in poorer light), poised to take off, and then captured several views of it in flight. (Click on each image to enlarge it.) Note how the shape of the wings in flight contrast with those of the Red-tailed Hawk.