I introduce newbies all the time. Infact, I am introducing my 5-6week olds to my POL as we speak. Just make sure you observe strict quarantine for the new birds before you do this.
I have two methods of intro. For adults, I have a small 8ft x 3ft x 3ft run butted up to my large coop. New adults go in there after quarantine for 1-2 weeks with a devider depending on the bird to be introduced (intros always go better with multiple newbies). Once the new bird is comfortable, I remove the divider so that the flock and the noob can enteract through the fence. Once everyone is comfortable with that, I slip the noob onto a roost in the dark, and watch carefully the following day. I keep everyone locked up for a week or so to observe interactions, and to make sure the new bird knows where to come back to roost at night.
This is the adult intro pen. Durring the first part of the intro, there is a sheet of corugated metal that goes between the small pen and the big coop/run.
For babies, like what I am doing now, I plunk down a removable pen in the middle of the coop, put everyone in it, give them a place to escape incase the big girls breach the pen, and make sure everyone has ample food and water until it is time to take the pen down. Because I put them out little (my current babies went out at 5weeks), I keep them shut away until the babies are big enough to be too much effort for a hawk to try to carry one off. By then, they have been out there long enough to know where to return at night, and they have been interacting with the "elders" for long enough to get along pretty smoothly.
I stretch a piece of tarp across this "pen" normally, but couldn't find it this time...Sammie decided to help.
