I have had my chickens for 9 years, we have never lost any due to overhead threats. Hawks owls etc. we use fishing line above our free range and coop area. In this picture with the ice you can really see the fishing line, and the ice is so heavy it is really low, but once the ice is melted the line will pop back up high. We put the fishing line in a spider web formation, and the birds see it and won’t come down when they see their wing span can’t get in and out of the web.