I have to respectfully disagree. I have appx 19 chickens, and I live on six wooded acres. I have two dogs, and they are house dogs, but we have a fenced in yard for them that they can run around in. The hen house is on the outside of that fence. They have a nice, covered run, but they do free range all day. They know the dogs are dangerous, and they do not go into their yard. I don't keep dogfood outside, but our veggie garden is inside the dog's yard, with a smaller, chicken wire fence around it to keep the dogs from trampling the plants, and keep the bunnies from eating the veggies.....
Anyhow, my neighbors also have dogs that are chained up, and they seem to sense that they shouldn't go near those dogs, and so far they never have. I've had chickens for three years now. The older ones seem to teach the younger ones about the safe boundaries, or maybe they do have some instincts.......I am not sure, but the fence is 4 feet high, and we haven't lost a chicken yet because one flew over. They do seem to know better.....
That is just my personal experience.