Introducing

[DottieJanesdad]

We have 5 chickens in the main coop (one is a bantam) and we also have 6 pullets in a separate coop that is right against the run. When can we put them in the big girl coop? They are about the size of the bantam and are about 7 or 8 weeks old. We do not free range.

 

[Blw18]

It depends on the temperament of the adult chickens as well as other factors but if it were me, I’d introduce and watch to see how things go. If it goes good, allow them to mingle for a while and then if there’s no issues, try it a little longer the next day with supervision and so on and so forth. Maybe just a little at a time until they’re just seen as another flock member and ignored by the older hens. Assuming adults react negatively, which is expected, as long as it doesn’t get ugly and the young ones have space to get away, I’d let them get to know each other under your supervision so you can break up any issues that happen. Otherwise, I’d wait until they’re big enough to take some pecks and find their way into the pecking order on more level ground as far as size goes. Space has a lot of influence. I have a lot of pen room having lots of personal space makes a big difference so they aren’t all on top of each other and have space to move out of the way if they have to.

 

[aart]

Here's some tips about.....
Integration Basics:
It's all about territory and resources(space/food/water).
Existing birds will almost always attack new ones to defend their resources.
Understanding chicken behaviors is essential to integrating new birds into your flock.

Confine new birds within sight but physically segregated from older/existing birds for several weeks, so they can see and get used to each other but not physically interact.

In adjacent runs, spread scratch grains along the dividing mesh, best if mesh is just big enough for birds to stick their head thru, so they get used to eating together.

The more space, the better. Birds will peck to establish dominance, the pecked bird needs space to get away. As long as there's no copious blood drawn and/or new bird is not trapped/pinned down and beaten unmercilessly, let them work it out. Every time you interfere or remove new birds, they'll have to start the pecking order thing all over again.

Multiple feed/water stations. Dominance issues are most often carried out over sustenance, more stations lessens the frequency of that issue.

Places for the new birds to hide 'out of line of sight'(but not a dead end trap) and/or up and away from any bully birds. Roosts, pallets or boards leaned up against walls or up on concrete blocks, old chairs tables, branches, logs, stumps out in the run can really help. Lots of diversion and places to 'hide' instead of bare wide open run.
Good ideas for hiding places:
https://www.backyardchickens.com/threads/a-cluttered-run.1323792/

 

[Ridgerunner]

The size and layout of your main coop is important in this. So is the size of the run. Knowing how big they are and what they look like could help us come up with something specific to your situation. Without that information Aart's generic comments are about as good as we can do.

Until my pullets mature enough to join the pecking order, typically about the time they start to lay eggs, they avoid the adults. If they invade the personal space of the adults they just might get pecked. They are typically smart enough to avoid the adults as much as they can, day and night. Each flock and integration is different. I have had some exceptions where they safely mingle a fair amount, even at a very young age, but the general rule is that they avoid the adults day and night. Sometimes these things go so well you wonder what all the worry was about, sometimes it can be a disaster.

Since one of your adults is a bantam you cannot use the safe haven/panic room concept. My approach would be to try letting them mingle during the day when you can observe. See how it goes. Let them mingle during the day where there is no drama or conflict for a few weeks. Give them time to really get used to each other. Then lock them in the main coop after dark with the adults and be down there at first light to see how it is going. That's how I do mine.

Sometimes mime put themselves to bed in the main coop after me doing that one time. Sometimes I have to do that for several consecutive nights before they get the message. My main coop is big enough and has enough hiding places that the young ones can avoid the adults. It's pretty standard for my juveniles to be on the roosts while the adults are on the coop floor when I go down to let them out. That's a good place to avoid the adults. I don't now how big your main coop is or how it is laid out. Your roosts may not be high enough that they ae a good place to avoid the adults.

My main suggestions are to be patient, let them work things out as much as you can at their pace, and go by what you see, not what some stranger over the internet like me tells you. We are all unique with unique facilities and flocks.