You just got to make sure you have a closed area for at night as chain link and most other fencing will allow all mink, weasel, rats, good sized snakes and many other smaller critters direct access to birds. Most can get through a 2 inch opening easy.
they will go through it, over it, under it, chew threw, what ever it take for a meal...The more secure you have it the better, we have plenty of black bear here and with-in the past 6 years never had any bother our coops..gues it isnt worth there while to gain accesses. of course we also have motion censing lights all around our coops to which i believe helps ward of critters to..
Here Our coops/houses that are attached to are runs all have small coop doors that are closed up tight each and every night, this is somthing we made a habbit of not forgetting to do.....we never once relax on this issue..
also When are coops are cleaned every 2 months we always inspect the coop floor for any possible chewing of these critter trying to gain access...
With fall and winter coming, alot of young critters will be looking for easy meals..that is a fact...be ready...If not secure somthing will sooner or later gain access..Like the old timers always said to me, if you protect your chickens at night, they will be there in the morning..
Here is a pic of one of the small doors leading into a run area...
back view pic
Charlie