[Thompson24]

How old do chicks have to be before they can go back in with the rest of the adult chickens (if they have been incubated?)

[Roughlee Handled]

Once they have been icubated and hatched they would then go into a brooder for five ish weeks, decreasing the temp from 37.5c to the out side temp by about 5c a week.
So your answer is 5 ish weeks depending on the time of year.

[chickenlady]

Personally I would say once they are nearly as big as your existing flock! otherwise I would think they would get picked on!(more than new girls of the same age as existing flock) I have a completely seperate run for all my new babies when they are big enough to go outside! Then when they aprox 12-15 wks they should be able to hold their own! my bantams have a new run all to themelves as dont want them in with the other girls! (counting my chickens before they've hatched again!)

Debbie