Mine only free range when I am home, and I keep at least one window open if I am going to be inside the house. Two warning geese are on the premises, as well as a house-confined Great Pyrenees. Pearl will not allow a squirrel to cross the yard undetected. (Why my livestock guardian lives indoors is a whole other story).
We are surrounded by farm fields and a small grove of trees; the chickens believe they are confined to the south side of the property (there is a 2-foot fence that prevents the runner ducks from wandering to the north yard but could easily be overcome by any of the chickens).
The area where the chickens are free includes several trees with large canopies, an always-open coop and heavy plantings of flowering shrubs and vines. So, there are plenty of hiding places.
The area is rife with predators. I hear coyote serenades all around us at night. There has been one fatal mink attack (which is why there is now a fence. After getting into a chicken coop when I forgot to close the door, the mink went after a wandering runner duck who strayed too far from the house). Two years ago, I thought I was feeding a fairly pleasant feral cat in the hay shed; turns out a possum was sneaking in for dinner, too. He smiled at me and hissed when I discovered "Cheddar" wasn't my only diner. I had to trap a rat this summer who holed up in a tree hollow near one of the coops. And, the DNR had to remove a juvenile great horned owl. The officer suggested she had knocked herself silly on a power line when she was stalking my ducks.
Still, the chickens' and ducks' delight at hunting bugs and searching for whatever goodies, to see them play and react in a natural environment is good for all of us, I think.
Having said that, the American Buff geese spend their days in a very large tractor and their nights in a coop. Gussie and Golly, who are about five months old, are pretty tame and pleasant. However, they can and will go over the 2-foot fence. I am hoping that as they get older, they will -- as some of the hens did -- learn to play inside the lines.
After the mink attack, I was terrified to let anyone out -- ever. My solution was to beef up security with hardware cloth everywhere and more vigilance on my part. The reward is watching my ducks -- in a row -- parade across the yard or see the chickens play keep-away with worms they've pulled out of the grass.