Getting My Chickens To Accept New Flock Members

Hello. I am a newbie urban chicken person, and until today, I had one pullet Orpington hen and two pullet Silkie hens. They've been together for about 6-8 weeks now in my backyard coop and run. Today I added three more pullet Silkie hens to my little flock. The new hens have been in with the chickens I already had for about 4-5 hours now, and the 3 of them still seem terrified of the other three chickens. They are mostly staying huddled together on the far end of the run, while my Orpington and other two silkies are strutting around the coop end, seemingly making it clear that the new girls aren't welcome. It's colder here today and will definitely be cold tonight - down into the 30s. I am concerned that the "old" chickens aren't going to allow the new ones to get up into the coop/nesting box area for the night. The 3 chickens I already had get up into the coop at dusk each evening to settle in for the night, and I close the door so they are safe and warm til morning, when I let them back out into the run. They have free access to the coop/nesting boxes during the day. What do I do if the chickens I already had won't allow the three newbies to be in the coop for the night? They've chased and harassed the new pullets quite a bit since I put them in the run, and I am afraid they could hurt them if they pecked them or otherwise went after them in my small coop (just enough room for 6 chickens to nest comfortably - no room for running around in there.) I welcome all feedback. Thanks!