The worst predator is other chickens, followed by sheep! I have never lost a bird to anything other than another chicken, ( older birds killing chicks, or roosters killing each other), and we had one hen get trampled by a sheep this summer. Our birds free range, we live in a rural area, but, they go in the barn and night and are securely locked in . The only thing I worry about are hawks, but we have not lost any yet. I'm never sure how people lose birds to mammals, the only thing that could get my birds is a man or a bear during the night. Here are some of the secrets..1) have shelter available for free range birds, we use pallets on legs, plus lots of spruce trees. 2) keep aggressive roosters , my main boys will stand up to anything, anything that comes near the hens. 3) keep 4 legged grazers with the chickens, just having something bigger around helps, and, the chickens are smart enough to follow the sheep and goats around. 4) GET A GOOD DOG!! We do all the above, and we do not lose chickens to predators!!!!