We just built a new coop and have not completed the enclosed run yet. Our girls mostly free-range in our fully fenced in back yard anyway. Over the weekend had some song birds go in the pop door and scratch around on the floor. I assume that they have avian lice, mites and whatever else diseases that I don't want my chickens to have. My DH thinks that if we put some fabric strips over the pop door opening that the chickens will go through, but it will deter all the little birds (sparrows, etc.). I was going to try this approach this weekend when I have time. Any other ideas or thoughts about this?