Red_Rose
When I went to pick up my gouldians, the people who let me inspect their gouldian cages, had a Parrotlet.
Although it was obvious the bird was very familiar with its surroundings and the mirror had been there for ages, the bird jumped off his shoulder and right smack into the mirror. It was stunned for a few minutes.
I'd try and think of something creative with your "curtain" and by all means put one up. Maybe a swish-curtain with some greenery on the side, or dried branches, so you can easily let the curtain go over the mirror when needed, and the bird has a focal point on the side to allow it to know where the perch is beside the mirror.
He hit that mirror so hard, Bill and I thought he was injured.