The way that people in the past protected their flock was that without remorse or limit they killed anything and everything that posed a threat to their chickens. That's what the old timers did back when free range chickens was the norm, say in the late 19th Century
A good coop or pen is nice but remember, a coop will work 99% of the time but that predators are only looking for that one time out of a hundred where there was a slip up in security.
No predators equals no predator problems 100% of the time.
Another thing to consider is an integrated pest or predator control or management program like commercial farmers use but this assumes that you will persecute the predators preying on your chickens only once the predators have killed a sufficient number of your birds that the financial loss has become to severe for you to bare.
No real farmer ever expects to kill every boll weevil in their cotton patch and no intelligent home owner ever expects to kill every chinch bug in their lawn but the Idea of INTEGRATED PEST MANAGEMENT demands that you kill enough of the pests or predators to get buy, therefor you still have losses. Even as a young boy when my family kept 1,000s of caged layers in secure chicken houses we still had loses to predators. Not a lot mind you, but some.
FYI, management means that you only kill enough of your predators/pests to get buy while control carries with it the idea of killing all the predators and pests then asking the all-mighty to sort out the innocent from the guilty.
