Established chickens picking on newcomers..Help!!

It's the pecking order. They should sort it out in a day or two. Watch for signs of picking and blood, but let them sort it out. Separate them if you need to.

 

Probably pecking order. Here's a link that might help.

Buff Hooligan’s Adding to your flock
https://www.backyardchickens.com/web/viewblog.php?id=2593-adding-to-your-flock

Age of the chickens is important. If they are too young, they are in more danger. How much space they have is important. It really helps for the new ones to have enough room to get away. Having separate eating and drinking locations for a while also sometimes helps. The older ones can be quite territorial about those things.

 

I've had much better luck with keeping them separated, but visible for 3 weeks, then a gradual introduction. It is perfectly natural for them to pick on a newcomer, who they see as a threat and usurper of resources. I would pull them back out and proceed more slowly, unless they iron things out soon! They can kill a newbie.

 

I'm having same problem, but no actual damage so I just keep waiting for them to figure it all out. The newbies won't go to the roosts at night. They just huddle in the corner. We built additional roosts but the older ladies just took those over too. If a newbie even comes close - watch out! They get all puffy and intimidating looking. Each morning I see them all wandering together on the floor, but each evening we go through the same thing. It hasn't been a week yet, so I'm trying to be patient. Those bossy girls are so frustrating!

I had 14 BO (4mos old) and am introducing 10 BO, 3 Plymouth Rocks, and 4 Comets (all about 3mos old). Having fun being overrun!

 

Forgot to mention that mine were separate but visible for a few weeks. They free range all day for now, but as they get closer to laying, I plan to keep them closer to the coop. The daily freedom seems to keep the pecking order issues to bedtime.