I just really started to seriously investigate the necessary things for having chickens. I plan on getting my first chicks this spring. Anyways, in my investigation I found I need a coop. I also saw many coop designs! All of them have doors and some with automatic doors. I'm wondering, if the coop has an entirely closed in pen/run (not sure the proper terminology, sorry) then why does there even need to be the door? I mean you've got the coop with a little door that they naturally go into at night, and if their pen/run is totally enclosed and safe, then why the door? Why not let them naturally self regulate. Keep in mind I'm a TOTAL newb to this, and I really appreciate any and all help!