A specific genetic mutation causes these chicken to have some astounding crests but it also causes skull malformation with 'vaulted' skulls like a large raised bubble of thin fragile bone, ridded with holes or even the bone on top missing altogether.
Very interesting to read.I didn't know about their defects before " made by humans".Now I'm happy that I not decided to have them.My parents have 6 wonderful "Swedish flower chickens "this year.Beautiful birds.