The mother hen knows the best integration strategy. Sometimes here the mother will just march the chicks back to the flock coop at three or four days old. Sometimes the chicks are hatched in the flock coop and this saves a lot of integration problems later.
I’ve had hens wait until a few days before they abandon the chicks before they take the now pullets and cockerels back to the flock coop.
I’ve had so few problems with the hen doing the introductions and integration.
There is one problem to be aware of. My coops are off the ground on legs. While mum knows how to climb the ramp, chicks often have problems working this out. They see mum go up the ramp and when mum starts calling the chicks to join her the chicks tend to go closest to the mum’s voice which is of course under the coop. Mum comes back down and tries again. If the mother can’t get the chicks to follow her up the ramp then, depending on the mum, she may just leave them; this can be a problem. I put the chicks in the coop with mum in this case. Watch out if you do this because the chicks give a distress call and mum comes out of the coop in full battle order!
Sometimes the chicks don’t go in and mum comes back out and sits under the coop with the chicks under her wing. She will stay there all night if necessary.
I put them all in the coop at this point.
You may have to do this for a couple of days. Eventually the chicks work out where home and mum is.
Some of the things that influence when and how the mum integrates the chicks are; where she (mum) is in the hierarchy, (more senior hens have fewer problems), whether the group rooster is the chicks father, the available space in the coop for the mum to protect her chicks from other hens usually.
The quicker the chicks integrate the more they will learn and the better protection they will get by being in the flock.
A mum out on her own rearing chicks makes me very nervous.