My main flock was killed by bears last October. I had two hens left. They are/were living in run and coop#2. I bought 26 new chicks in January and put them in coop #1. After a few weeks I would free range the new kids by themselves (the old girls too, but at different times). As the time rolled on I started to let them all free range together. Because of the large space they did ok together. I have one old hen that is nasty and would chase all the new chicks. After free ranging them together for 2 weeks I found that one of the old hens would go into coop #1 to roost in the evening, and she is the nasty one! So it looks like they have made peace and integrated nicely. The 2nd old hen still returns to coop #2, but that's ok. I think pretty soon she will be with the others! I like the free range method to integrate because it gives the chickens room to run and get away. Eventually they work out the pecking order and everyone gets along. 
