It's true. I used to have a canary as a pet, so I know from
experience. When I first got LB, she (or he, I was never positive of
my canary's sex and didn't want to check) the
bird cage was in the hallway next to a big mirror and in the
morning when I took the cover off of her cage (I needed to cover
the bird cage with a big sheet at night, otherwise she would
never fall asleep), LB would fly around a bit, stretching out her
wings and then notice the canary in the mirror and get
really, really upset. She'd tweet and twitter and puff herself
up into a big, orange ball of feathers to try to scare the mirror
bird away (maybe she was a boy) and when that didn't
work she'd angrily try to attack and crash into the side of the
cage. She only did it for two or three days because, my mom made
me put up a scrap of wallpaper between the bird and the mirror, but
that's why I think that holding up a mirror to a little bird is mean.