My son and I got 10 Chickens 1 Rooster. A friend of his has chicken houses and gave him them at 4 weeks old.. We have had them 3 months and they are very big. new he has accumulated 10 road island reds, and 5 dominickers these are babys still not but 4 weeks old and little compaired to the others. how do i put them in with the other chickens, with out them getting hurt and how old do i need them to be before i do it. Any advise would be helpful.