Bird Maniac:
True free ranging.......no fences.........no borders.......is almost always going to result in a bunch of dead birds if you live in an area with a high predator load. Predators have to eat and are really good at finding and killing prey. Your birds will be easy to find, easy to kill prey. So once predators find them, they mostly focus on them until they are all gone. I asked my folks once what the old time farmers used to keep birds alive and the response was everyone kept a mean dog. An outside dog. Watch the old Foghorn Leghorn cartoons to see the role of that dog. A lot of folks on BYC still do keep dogs for this purpose.
But even then, as it is now, folks who free range, even with dogs, still lose a lot of birds. Birds go everywhere and the threat is constant. No animal or person can be everywhere and always at the ready to intervene.
So predators win......almost every time.
What you may also want to consider is to establish a zone of protection out on the perimeter. To do that, you use an electric fence.
https://www.backyardchickens.com/threads/dogs-and-electric-fences.1210854/
Properly built, properly maintained electric fences really do work and are one of the best options for safely opening up a large area to allow the birds to roam around in relative safety. Fences of any type offer no protection from hawks and other raptors, but do work for most of the ground based stuff....at least during the daylight hours. You also will need a bomb proof coop to protect your birds at night. Where most fall down on that end is not realizing what bomb proof means. It means heavy duty.