My ex-cockerel (8-10 months I think? He went to live with a neighbor who has since moved) would do his deed with all the ladies he could get, too, and if he saw another male come into his territory, he would literally chase him until he could mount the poor screaming rooster. I had one poor guy who would start screaming as soon as he say that brahma heading his way. It is one way (albeit less common than fighting) that the males express dominance over other males.