I keep finding one of my chicken brooding on piles of rocks in her nesting box. I take the rocks out of her nest, then about a week later its full of rocks again. I have literally filled buckets with her rock "eggs"!?! I would never have thought a chicken could move rocks. These aren't pebbles either. They are the size of eggs. She a bantum brahma. Has anyone else seen this behavior? Is this normal? Is she just a rock freak? Should I be worried? Thoughts?