Three weeks, in three weeks he can go outside but the others may reject him so he will be a loner for a while, but once they get over it. BOOM he'll be in the pack. When I had my second batch of call ducks, my first group would constantly constantly attack the second group, but then when the third group came in now the first and second group are one HUGE group. I exspect the third group to be joined in soon now that the Mommy from the first group has seven babies. LOL.. Seems like all new groups get rejected for a while until a newer group comes in the picture..
They grow up soooo fast, at three weeks they start getting there adult feathers and lose the baby feathers, just on the wings and tail... The rest will come in later..
Good job and good luck with your new guy. LOL..