I was collecting the chicken eggs a few days ago, and I saw one of my hens eat two feathers off of the ground. Over the past few days, I have noticed all of the chickens doing this. It grosses me out a lot, and I am wondering WHY they do that. They eat Layena free choice and the occasional grapes for a treat. Is there some kind of nutritional deficiency causing this? What can I do to get them to stop, or is it just natural? Thanks for the advice!