Can you fence off an area of the yard and use avian netting? I have a 40 x 40 foot fenced pen with avian netting on top and that stuff is apparently quite strong.
A few days ago a heavy tree limb ended up on top of the net and rested on the ground, after my lawn man and his grown grandson helper got it OFF the net with a bit of struggle no damage was done. Tuff stuff! Pretty cheap too, cost me $60 or so on Amazon. Keeps hawks OUT and my bantams IN.
If your chickens start roaming outside of your yard they will become prey for something or other, cars, dogs, something.