My Slyvester is invaluable when it comes to hawks. I only let my chickens free range when I am out and about but that doesn't seem to stop our red tails from trying. Like I have said before there is one red tail that is friendlier than some of my hens. Anyway, he always sounds the alarm for me and his girls when he spots one, gives me a chance to pick up a stick and the girls the opportunity to RUN FOR COVER. The great thing about Slyvester is he doesn't give out very many false alarms. I have had roosters that give the hawk warning call at the sight of a sparrow passing through and the hens get to the point in which they ignore it.
Now Slyvester can't resist if one of his small banty girls gets a spurt of energy and flies across the yard for fun, I think Slyvester is just cheering them on though.