I have seen blue tits tapping my bedroom window - thought they were just winding up the cats!
Yes we have had birds attack the wing mirrors on our cars too. And they nibbled the rubber around the side windows on ours and our neighbour’s cars.
This behaviour is not uncommon. He sees his reflection and thinking it is another male, he is trying to drive away this rival from his territory. Not a potential mate as suggested above. The behaviour will stop as soon as the serious business of actually nesting is really underway.
An old neighbour had a pied wagtail attacking his wing mirrors so often, he took to putting socks over them.
I used to have mallards peck the windows to encourage me to feed them.
EVERY YEAR IN FEBRUARY WE HAVE THE SAME PROBLEM WITH A CROW.
I THINK IT IS THE TIME OF YEAR WHEN BIRDS ARE PAIRING UP AND CHASING OFF RIVALS. OUR OLD LAD OBVIOUSLY DOESN’T LIKE THE LOOK OF HIS.
I JUST WISH HE WOULD CLEAN HIS MUDDY BEAK BEFORE HE STARTS. DOESN’T HALF MAKE A MESS OF THE GLASS.
I agree with Dove. The chickens at my workplace tap on the glass too, probably thinking there's another chicken. Quite funny to watch.