Just wanna add a little from my experiences. Young roosters, like under a year, and any hens/pullets, are a danger to chicks. Mature cocks are great with younger birds of most any age. Most mother hens will do their best to protect their young until they are weened, which is after they are feathered as stated above. Some are not capable, but most are. I base this on years of penning my weenlings with a mature cock so he can police the young game stags. The idea is that if anyone is gonna kick butt, it`s gonna be the cock. The cock is almost without exception, great with young birds. It`s worked well for me for a lot of years. I can usually keep the little killers together til they are 7-8 months old. There are exceptions, but just watch your chicks around young cockerals and females........Pop