Then hens can be real mean , in my experience. i would take them all out of their pen if you can, and introduce them in a separate area. Or possible take out the older hens, introduce the new hens for awhile and then add a older hen, one at a time. It all really depends on their personality. I have had easy going hens, then I have had out right mean hens...... but she was raised by me. but this is just my experience.
Wait till everyone is the same size.....throw the new birds in at night. Not sure what your pen size is but if the pen is big enough with enough cover you should be okay. I will be adding some new hens to my exhisting group today as well.
Most hens are meaner then the roos when adding new birds what works great for me is i made a cage small enough for me to carry i would put the hens in the cage and place it in with the older hens so they could get use to the new ones with no one getting hurt and most of the time in a couple hours i would turn them in with the rest and still no fighting.or just place the cage out side of the pen.this has always worked for me.
Bigger pen is always better,but when introducing new birds to your flock,they all should be placed in a new pen.The birds in your pen have their pecking order,and if you intoduce new birds they will defend their space.In a new pen everyone is on even grounds.
Looks like the move went just fine, I moved some of the older hens so the younger batch out numbered them about 2 to 1, added some extra brush for them to hide in. There was a little bit of fighting at first then they settled right down. Once they got used to each other I put the rest of the older ones back in. That was way to easy, the new batch must be defective since they didn't all try to kill each other.