I know you're getting all kinds of good advice on fencing, etc., but for me, the very best thing to prevent predator attacks, has been my dogs. When i didn't have them, i had predator attacks all the time, and now i don't. A good dog who can be taught not to bother your chickens is priceless. Mine are mutts, but they don't let anything near this place, and they don't hurt my chickens either. I never worry about my chickens while they're free ranging.