A not-so-smart pigeon flew into a window during one of my classes back at the University. The classroom was very quiet at the time so the noise seemed too loud. I remember actually seeing the bird sliding down the window - maybe it fainted or something?
Another time, when I was doing my MSc and had an office, another pigeon flew in from the open window. The whole wall was covered in windows and they were all open except from a small narrow one on the far right side of the wall. Imagine where did the pigeon try to exit from for a couple of times before finally getting out.