I have a Barred Rock chicken that just will not get out of the nesting box. She dose not lay any eggs but her two sisters lay like crazy they are all last spring's chickens. I pulled her out of the box and brought her inside and she sees happy and healthy. Her tail is up and really triangular compared to the others. I cant find anything wrong with her. It has been very cold but they have light and their water has not frozen so they are all warm. Any ideas?