i have two australorp hens that are suddenly developing bare necks. i just noticed this in the last 2 days. we have 14 hens total and 1 rooster. they are free range. even in the cold of winter they go out a little bit, and when there is too much snow they have roam all around the barn and are not in their coop all day. there is no fighting or pecking. their food and water is easily accessible; that was my first thought that they might be sticking their heads through something or rubbing against something to cause feather loss, but i can't imagine what it would be. any other thoughts? what could be causing this?