Generally, at what age is a rooster old enough to start breeding? I have a flock of EE's that are about to start laying and I have a few BCM roos that are currently 4 weeks old. The ones with the best coloring will stay with my best BCM pullets and the others will be added to the EE's for Olive Eggers. I plan to introduce the roos to the EE's around 16 weeks. Once the upset of new chickens is over can I expect the roos to start mating my hens at that age or do they need to be older?