I can tell you, from first hand experience, that when a Red Tail wants to come after you you need to get out of the way!!
There are several Red Tails that nest in the woods across the street and one afternoon one of 'em decided that my presence in my front garden was no longer to be tolerated. Low level, straight at my head, talons out. (I ducked and it missed - probably intentionally) But it left me a nice, big feather.
(We also have Red Shoulder hawks - they are truly amazing as they zip at low level through the trees.)