Of the feathered variety.
I’m trying to work today, catch up on stuff that didn’t get done at the weekend due to new-toy obsessing, and this little critter is doing my head in. He’s been at it for the last couple of days. I reckon he’s fighting his reflection or summat.
I think he is trying to tell you something, but I am not sure what…
I think that is a dmoesticated finch of some kind.
Alternatively and more likely its because you’ve superglued trill to your window.
Told you your new bike would have the birds flocking
Mate if he does it again get the air rifle 
Is there another window in his line of vision? So that he can see through the house? Usually when they do this, it’s because they can see through two windows and don’t realise there is no flight path. The way to stop this is to tape a cut out shape of a hawk on the window. Please do this before the poor thing hurts itself.
If it hasn’t hurt itself yet I don’t think it’s gonna. And I shut the door today after thinking about that this morning.
No change.
He just A CRAZY BIRD !!!
Best get the scissors and sticky back plastic out then.
LOL, looks like he is defending his teritiary, against his ermmm self.
cute little thing…
Ever thought he was knocking becasue he wants to come in, maybe just to say hi, relax with a coffee, maybe just keep warm or play hide or die with your cat etc 
Quick, shoot the little feckar before ya get the bird flu. he he he.
Once had an owl fly into our patio window with such a force we had an owl shaped imprint left on the glass. Poor little begger must have knocked itself out.
