I had this happen at my place a number of times, my house is up on a hill with large windows facing the view. I didn't want to put stickers or other things that would detract from the view. A neighbor mentioned that they put up a couple of decorative hanging plants off to the side of the windows, didn't have to be right in front which would block the view. I opted for a couple of hanging outdoor art pieces (I have a brown thumb). It worked, my theory is it gives the birds something to gauge perspective on perhaps. I am not sure how that could work for skyscrapers, but for a home like mine it worked like a charm.