We believe this is an immature "Red Tailed Hawk", images 1 through 19 in this gallery.
Thank you, Ron Lambeth, formerly of the BLM for the State of Colorado, for so generously identifying these birds.
Here is a quote from Ron: "In that gallery it looks like photos 1-19 were red-tailed hawk photos and numbers 20 to 25 were golden eagle pictures. Photos 6 and 7 are tricky, but the dark mottled top side still makes the bird to be a redtail. The immature redtail has the brown head and dark bar along the leading edge of the wing characteristic of redtails. The heaviness of the belly streaks and the thin bars on the tail are characteristic of redtail immatures. Note that I don't say juvenile. It's because I don't know juvenile plumage of redtails well enough to say that it is so young a bird. They are juveniles only a short time - weeks."
More images from other sources can be seen here: