I grew up on a farm and when I got old enough I borrowed an incubator and started a flock, I was probably 10. we had plenty of space for free ranging and my parents didn't want to pay high feed bills so I let them out each day, thinking it was night predators that were the likely problem. much to my dismay, we started loosing chickens, one by one. then one day after school I heard a commotion and ran down to the barn to see what was going on. I got half way down the hill and along came a hen, running for her dear life and after her was a fox, in broad daylight, it practically ran across my feet giving hardly a care that I was there. it was spring and likely finding food for it's kits. I was devastated and gave up with chickens shortly after that.
fast forward 30 something years to last year, I built the fort knox of chicken coops with hardware cloth wall to wall and across the ceiling and two feet into the ground, angled at a 45 degree angle toward the outside. we have a dog and kayotes, hawks and live on a steep hill, so unfortunately our hens have to be cooped up 24/7. I may create a fenced in area and give free ranging another try but I'm going to wait till my kids are older and can handle the prospects of losing some of our beloved hens.
I have friends who think I'm ridiculous and paranoid, telling me that they have been free ranging for "a long time now" without a single issue", only to then lose everything to coons with kits. hungry parents are a challenge, hungry parents desperate to feed their babies are amazingly persistent and bold.