My birds used to growl and attack their mirror so I had to remove it from the cage. I have brought a cheap bell before, I removed the clapper and used a plastic zip tye to hold a replacement parrot friendly clapper (an easily replacable parrot safe piece of wood).
I don't use mirrors in cages. The last one I used was for Chick Chick to talk to herself while she was laying an egg. I had a big mirror behind my sofa. We all got a big laugh when Myrtle landed on the sofa and said "Hello there Myrtle". Lucy dog, Fancy cat and Myrtle are the only ones I have witnessed identifying themselves.