We have been trying to integrate our three 10 week olds (Buff Orpington, Easter Egger, Rhode Island Red), and one 5 month old (Barred Rock). (We have a 3x4.5 coop and connected 3.5x10 run (they do not free range) When the little ones were 4 weeks old, we put a divider in the run and I would bring them out every morning and take them back to the brooder at night. At 7 weeks we tried putting the big chicken in the coop with them at night and pulled out the divider in the run. This lasted for about 2 or 3 days of slight nipping and aggression before the big chicken started really drawing blood from the runt (the Rhode Island Red). So still about 7 weeks old, we put the little chickens in the coop during the day with the big chicken on the other side of the divider. At night we would bring the big chicken into the coop and take her out to her confinement area in the morning. Absolutely no problems with this setup. We tried briefly to open up a section of the divider around 8 or 9 weeks, but the big chicken would still go after the runt. Now at 10 weeks, we tried putting them together again. Yesterday ~1230 we opened up the divider, and we had no problems at all (they actually all looked kind of happy) until today at 1530 when the big chicken drew blood again, this time from the Buff Orpington. I think this may have been spurred on by the fact that the waterer inside the coop was empty, so the BO had to come out into the run to get some water (the Barred Rock's territory). So. Do we just keep doing what we're doing? Keep them separated during the day, and every week or 2 try to combine them again until there is no blood? Do you think they would have been fine if I had not let the water go dry inside the coop (I think it's strange that they were totally fine for over 24 hours, and then all of a sudden the big chicken went on a rampage...)? Or maybe we just need to get rid of the evil Barred Rock... (I have an unhealthy hatred for that bird!). The three little ones get along great (there is no pecking even after blood has already been drawn), we just need to get the big one in line!