Polish Chickens have a very distinctive skull. It has a boney protuberance on the top of the head. Their brain grows into this protuberance and is hour glass in shape. The skull is delicate and very vulnerable to injury. Polish Chickens are also prone to head pecking both from other breeds and their own kind.: Photo of a chick who is in the process of hatching.  The unusual head shape shows clearly while they’re wet from hatching.  Illustrations;  A. Polish Chicken Skull. B. Normal Chicken Skull. Below the same chick drying and a sibling almost dry.