I have an Americana rooster and 8 hens (1 Americana hen and the rest RIR). We hatched two chickens and they were about 10 weeks old when I tried mixing them with our flock. After a week, I went outside in the morning to find one of them dead . I took the other one back inside where we have 5 other chicks that are about 5 weeks old. I am pretty sure that the chick that died was a boy anyways... is that why they killed it? I don't know if the other 10 week old is a rooster so I took pictures hoping someone could help. four of the 5 week old look like this, and there is also one brown one but i cant get good pictures.