We have a variety of hens black Marans, barred rocks, cuckoo Marans, Americauna,silver spangled,white and red leghorns,and a pioneer that thinks she is a dog. We have 22 nesting boxes up and our hens all use the same 3 boxes. They will literally climb in the box while another hen is laying. While it does make them easier to gather it does make it harder to keep the eggs clean. Why do they do this any suggestions on how to make them stop?