For two days, while I would use my computer, there was a tick, tick on the window. I wondered what it was, but did not get up to see. So, the second day, after it was going on for a while - like a half an hour, I decided to get up and see what it was.
Baby Sparrows on the outside window sill, fly back and forth into the tree and back to the window sill.... with one of them - tapping on my window with its beek.
Here is a picture of some of them.