I don't (or very rarely) free range my birds because of this. The best solution is a strong run with a top, even if it means having fewer birds. I've occasionally had a hawk do like those redtails you talk about and have done the things you said. Usually, when they find that they can't get anywhere, they give up. My daughter's idiot dog runs at the run barking when he's here, which used to send the chickens running. Now they don't even pay attention to him. If chickens could laugh, they probably would say ha!ha! you can't get us! Hopefully yours will do the same once they realize they are safe in the run. I hope you can solve the problem. I'm not an advocate for killing something for no reason, but when it attacks livestock on one's own land, then that thing is a varmint in my opinion. Some people say hawks have to eat too, but so does a mosquito and I don't know anyone who wouldn't swat one!