mixing old and new?

[clea]

I have existing 6 hens and 1 roo ( all 3 years old). My new spring chicks(9 hens and 1 roo) are now grown and ready to integrate. My question is HOW ?

 

[Mountain Peeps]

WELCOME TO BYC!!

As far as the best way to introduce, I've found that the "see-but-don't-touch" method is the most effective and less dramatic. This involves placing a barrier in between the two groups so they can can't reach each other but are still "around" each other. After about 3 weeks you can slowly mix them. Interfere if there is bloodshed or severe bullying. Take it slow.

Here's some links too.
http://www.the-chicken-chick.com/2011/06/integrating-new-flock-members-playpen.html
http://www.fresh-eggs-daily.com/2012/04/adding-to-established-flock-pullet.html
https://www.backyardchickens.com/a/adding-to-your-flock