I am raising my first brood of chicks this year, and have a summer coop (smaller, but very well ventilated) attached to a winter coop (much bigger, in a solid shed structure that is insulated for the Minnesota winters). The summer coop leads out to what I am calling the chicken gulag which will have welded wire garden fencing trenched down and out to keep out burrowers then additional chicken wire encasing sides and top... I have almost every predator available in the northwoods: dogs, raccoons, coyotes, eagles, owls, mink (yes, I said MINK)... the list goes on. SO, the question is, do I need to have a door on my coop's chicken entrance (is that what the term "pop door" means?) in the summer house to keep them locked in at night, or is the gulag enough to protect them? And, in the winter, can I give them access to the summer coop (and as such, the outdoors) at will, or are they, excuse the expression "not smart enough to come in from the cold?"