not all hens will lay a double yolker, must of mine never have. I have one hen that for 3 years laid double yolkers quite often, she's slowed down on the doulbe yolkers this year, but still lays reg. I took diff sizes and colors of eggs for my dd preschool class to look at and took one of hers that I thought was a double yolker, it turned out to be a double yolker with a tiny whole egg inside from what the teacher said.