We only have a few hens (no rooster) and over the past week I've noticed one of them being very strange when I let them out of their pen in the mornings. She is the head chicken (henpecks all the others) and she will be laying almost on her side, one leg spread towards her head, the other towards her tail and she is breathing heavy, seeming unable to move. I've seen this twice. Once she eventually got up, the 2nd I had to help her. Once she's up, everything seems fine. My father says she was like that yesterday afternoon as well. Any idea what could be causing this?