i just went out to check on my hens and i noticed something strange i have never seen them do. they pull in their heads close to their bodies and fluff up their feathers and kinda stand hunched. does this just mean that they are cold or is it something else. they just stand there and they pull back their heads and their feathers are fluffed then they kinda just close their eyes really slowly. then if i move they open their eyes back up and act normal. does this just mean that they are cold?