My 3yr old hen has been very sick and appeared to be near death twice. Her appetite is good. Now all of a sudden she started eating wood shavings, I should say devouring them. She is in a crate due to being sick and I have had to cover the bedding with a towel.. It seems like she is obsessed with them. What would cause this behavior? She has constant access to her regular layer crumble and been feeding scrambled eggs.