Mature hawks want to hunt from much higher altitude than that and in open air where they can attack anything within their vision and accelerate rapidly by diving to take it out before it sees them...with minimal energy expended by soaring the thermals to get to attack altitude.
A hawk that hunts close to the ground from within the confines of a tree makes more attacks than kills and expends high amounts of energy doing it making it a high risk to reward ratio. It also rapidly depletes the available prey within its narrow range of attack and is forced to move on to larger fields of attack and higher attack to kill ratios in order to survive.
