I have seen a few comments on birds and mirrors and thought i would share my experiance.
I had a big mirror behind her cage for ages and she used to sing, cluck and pose infront of her mirror. So I bought a little double sided mirror and put it in her cage and took the other mirror away.
Well she peaked!
fought with the mirror and made a hell of a racket! so I put it on the outside of the cage. Everything is cool again! now when she sees the other bird it's not in her cage, and watching her showing off to the other bird outside her cage is always cool.
Occasionally you hear her go off again, but she is always on the outside at the back of her cage fighting that bird, but it still is not in her cage! She also just climbs back up when shes happy she showed that bird who's the boss!
I believe she is enjoying having the mirror there now!