I just got my first roo and put him in with the girls. He is 9 months old and I'm not sure if he knows what to "do" yet, but I was watching him tonight for a few minutes and he acted like he wanted to mount one of the hens and my Giant Angora rabbit. I know I can just crack open an egg every now and then and look, but how long will it typically take for my hens to start laying fertile eggs?