As you are in PA, your winters are probably similar to ours in NE Ohio. Predators are much more active in the winter as their natural prey is more scarce. I lost two birds within 4 days of each other in December. During the summer months, I free range daily. During the winter, I use a welded wire run. Last year it did not have a top on it, we are definitely putting one on this year! Fox climb the fence, hawks fly down from above...a secure area for them to exercise, scratch, etc would be ideal in the winter. If possible, have at least a portion of the run covered with a solid roof to help keep the snow level down in the run. My birds are real..chickens! They are afraid to put their "dainty" toes in the snow!