I grew up on a farm-we would get 100 chicks each spring. My parents watched these chicks as they got rid of their fuzz and started growing feathers. My Father would move his hand over the chicks to find the males and band their leg. The chicks that would go after his hand and try to peck it were the males, the females would act like they were nesting or afraid of the hand,

These young Roosters at a very young age start fighting each other for control of the flock, at that time my parents either traded to farmers who needed a rooster or as Jim said-KFC.