Always add new chicks to an already-existing flock when the chicks have reached the age where they are the size of the grown birds and they are able to defend themself. Chickens are intelligent birds with a complex social hierarchy called the pecking order, in which every chicken has its own ranking depending on how dominant or weak it behaves. It is totally normal for fighting to happen when new chickens are mixed into a flock-in fact, there is never not any fighting, since chickens have to determine each other's place on the pecking order every day. That being said, you should still monitor them. Any excess bullying behavior should not be tolerated. Be sure that you let the new chicks see the old chickens before letting them in with each other-this is called the "see-no-touch" method and is used in many situations.But is it difficult to add new fluffballs to an existing, grown flock?
Sue