I have 5 Barred Rocks that are 15 weeks old. They have been in the coop for the past 3 months. The girls took to the coop very well for the first 2 months, but this past couple weeks they have been sleeping outside on a roost. We do not have a door on the coop entrance. It just leads out to a 12' x12' run that is 7 feet high. The coop itself is built inside a large shed that holds all the feed and supplies for the chickens and our other animals. The shed is well secured with a concrete foundation. The coop itself is 24 square feet.There is food, water, nesting boxes and roosts in the coop with proper ventilation and light. All five birds have now been roosting every night on a branch that runs the width of the coop (12 feet) and is about 5 feet off the ground. I have tried to physically put them in the coop and bribe them with food and/or treats, all with no luck. I have cleaned to coop out, inspected it for any possible unwanted guests only to find it all clear. So far I have been just letting them stay out at night, as the run is secured to prevent anything from getting in or out. (The run use to hold our hunting dog who was quickly renamed Houdini) Does anyone have any suggestions on why they would do this and if there is anything I need to do? Thanks!