I have a similar age cockerel in a pen with three older hens,and a bunch of young pullets his same age. He's terrified of the older girls still! I just noticed him giving a warning call for the first time yesterday, so he's not really mature enough to mate. My older hens have high standards for a rooster, so they're going to make him work for his mating. I'm not worried about things until spring,and I'm pretty sure by then I'll have excellent fertility