Free range means they're free for every passing varmint too.
I live in a forested area, which means that predators get very close to my coop and birds since they do not have to leave cover to do so. THey feel quite secure lurking around, not exposed out in the open. If you free range in wooded area, be aware that you will have some losses. That's just the way it goes. Everyone loses chickens to predators of one kind or another. But heavy woods means bigger predators are more securely hidden...you might have bigger problems.
My chicken yard is not made of chicken wire, but heavy gage fencing with chicken wire overhead. The bottom 18 inches of the pen is 2x6 boards, solid. This pen keeps out coyotes and raccoons sometimes. IT will not keep out bears. Bears pretty much destroy anything they decide to destroy.
What I'm trying to say is that free range or not, your birds are vulnerable and having them in bush makes them easier for some predators to get to. Lock them up at night and watch the sky. If you let them out one day and you hear/see hawks overhead the next day, do not let them out. Mine have about two days in a row outside the pen before flying hunters show up. Good luck!