The only thing I know of that helps with feathered predators is some kind of covering whenever they are outside. Some use netting (I use deer netting, it's cheaper), some use large fishing nets, some use chicken wire. Some even run string back and forth eventually making holes that are too small for the hawks to get through. But they must be covered to protect them from what comes out of the sky. Some people with large flocks just let them loose but provide lots of bushes and things for them to get under, but since you want breeders, I'd just cover the pens. It has worked well for me. But I still lock them up securely at night ever since I had an owl sit on a post and tear the netting. It got in and took 2 beautiful EE roos who were too stubborn to go in the coop.
