I have heard that chickens know when it is bedtime, and they automatically go into their coop at night. We live next door to a house where there are a lot of chickens, geese, turkeys, and peacocks, and they animals find their places when it gets dark (its really cool to see a peacock in the tree!). I waited tonight and had my girls in the run, with the door to the coop open. Nothing happened even when it was beginning to get dark. They stayed huddled under the coop. I let them out and picked them up one by one and placed them in the coop with the other door shut. How long will it be before they figure out that it is nighttime and they need to go inside the coop, on their own?