Check out the photo below ("click" to enlarge)...a juvenile Cooper's Hawk my friend Shyloh sent me. By the way Shyloh, your photos are fantastic! Anyway, notice how grayish the topside appears. Juveniles in fresh plumage often have a sheen on top and do not appear as brown as they "should", and for this reason they might be confused for adults if seen from above. Even during fall migration, some juveniles still lack significant fade or wear and appear "fresh". Of course the head lacks an adult pattern, but with only a quick glance, this mistake could and has been made.