That Door Again... and a visitor!

3rd Blip on the run that this door into the garden has been featured! Today our resident Robin decided to keep popping up at the glass and tapping on it - what it was doing heaven only knows, but with working in the room where the door is, it drove me a bit demented by this evening - all day it was tap-tap-tapping! Maybe it could see it's own reflection? Any ideas??