I have hawks, but thankfully have not lost any chickens to a Hawk as of today. I have to agree that a great Roo is best. Scooter who is calm and easy going in the coop and run is a different beast when out in the field free ranging. He will attack a dog, a cat, or anything that come near his girls. I have watched them and seen him make a noise and all of the ladies run over to the fence, then walk along the fence back to the chicken house. If they are all in the covered run, you can look around and almost always, you will find a hawk sitting in a tree some where.
He is a great Roo.