Looks like a Red Tail Hawk to me. Definitely a hawk though. We have two right around our area that I see quite often. They will sit in a tree for hours and not move at all, just scanning the fields. I had one take off right next to the car last summer along the highway. When it got airborn, I realized it was clutching a snake in his talon.
Must have been about 3 ft. long. Happened to quick to be able to take a pic. Amazing sight.