I started with 8 production reds that were 12 weeks old when I bought them. 2 died and now the others are 20 weeks old. Today I bought two 13 week old EE and introduced them to my other 6. It didn't go good. If I hadn't seperated them in 1 minute my 6 would have killed the new birds. I built them a pen inside the pen and will try that for a while. Any other sugestions would be nice