I usually wait until about 10 or so weeks. My biggest daytime concern is neighborhood (feral cats) and hawks, so I try and make sure they are big enough to be almost chicken size so the cats won't be tempted. I still usually lose a couple to presumed hawks, maybe cats, no sign, no feathers, no bodies.
@Kassaundra
Thanks. Since I only have 3 I don't want to lose any if possible!
What has been your experience with integration with the older birds?
I ask all this because the only times I have added to the flock previously has been with a broody. This is my first time integrating non-broody raised kiddos into an adult flock.