I have never understood chickens’ reproductive system, even though I have been curious about it for years and I always had access to a library. However, I have finally rectified the situation by the magic of the internet, and I learnt some fascinating facts. Did you know that avian sperm remains viable at body temperature? That is why a cock has no, well, you understand. The papilla, which is sometimes called a penis though it is not one, dispenses but does not penetrate. The testes are internal, as well. Moreover, the hen has sperm host glands that can keep sperm for two weeks. I thought only insects had such abilities. I also discovered that the “blood spots” that you sometimes find on yolks have nothing to do with the developing chicken. Rather, when the yolk leaves the ovary, it sometimes takes some of the blood vessels that surround the yolk with it. I also read that the hen mobilizes half of her body’s calcium from her bones to make egg shells, though I am not sure what that means. I surmise that a hen has a certain amount of calcium in her bloodstream that can be used in the shell making process, but perhaps she supplements this with calcium from her bones that she can replenish during periods of rest. That seems like a bad idea, but I am neither God nor a biologist. I suppose that it is an efficient use of resources.
I always suspected that chicken sex was cool. If you are similarly curious, the University of Kentucky has instructive sheets for the female reproductive system and the male reproductive system.