We free range all year, lose a few birds as would be expected. What we found to work for us is a electric fence. They are pretty economical and keep most things out. The chickens,turkeys,and guineas have learned where the 2 acre safe zone is and stay within or close to it. I run two wires, one at about 6 inches and the other at about 18. Some birds get shocked and others go through,I think the feathers insulate them, but any four legged creature soon learns to stay away. For the hawks I leave escape cover in areas(brush piles,corn patches, and tall grasses) that when the rooster gives the alarm they run to.
It's not 100% but works to our expectations.