My birds sleep on top of their coop instead of inside, but it is inside a large run covered with hardware cloth for the small critters and hog fence panels for the larger critters. Covered all sides and roof, 2/3 of roof covered with metal roofing, the other third with hardware cloth and hog fence. There is an apron of welded wire all around the outside to stop diggers, and im still nervous. The coop is built like fort knox with an automatic door that they wont sleep in. If and only if, you are 100% sure your run is predator proof, and your coop is inside, protected by it, you can be realativey safe leaving the coop open in case they decide to actually use the coop. And you will still worry.