If you have a pen, some people have reported that stringing fishing line across the top (back and forth, both ways like a spider web) will keep rapters from getting them in the pen. Other than that, make sure they have access to plenty of cover - bushes, cars, plywood on buckets, etc. for them to dive under when the hawk comes. If you have a roo, he will likely be viglilent now that there has been an attack. Some roos will fight a hawk, sometimes they survive the fight......but not often. I have hawks in my area and lose birds to them on a regular basis. I have never seen one take a chicken but have found the evidence. Usually, I will lose the smallest chicken, then the next smallest in a couple of days and so on for two weeks or so and it will stop for a few months. I am sure you are not willing to risk that many birds. You may have to keep them up a while.