Introduction of new birds to existing flock

[Burky]

Just got 4 more reds to add to 5 year old flock (of 4 birds). Had them separated but coexisting for 3 days. Tried to put two of the old reds in with new birds and they started hanging up on new birds. Pulled out the old reds and put in one barred rock, little pecking order stuff but not as bad as the reds. Anyone have input on what's the best approach? Ultimately I'd like them all to be together.

Thanks!

 

[Burky]

Old flock consists of two reds, one buff orphington and one barred rock.

 

[aart]

Had them separated but coexisting for 3 days.

Pretty short time period.

How old are the 4 new birds?
How big is your coop and run?
Dimensions and pics would help here.

This might help, 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/