Hi, welcome to BYC! I used to live in the mountains too, for about six years. I lived just outside Angelus Oaks, at about 5500 feet. I didn't have chickens then. I had horses and dogs. Bears were a real problem, as well as buku raccoons. I have also seen bobcats, mountainlions and ringtail cats. First thing to worry about rather than what breed, of chicken is how to predator proof your run.