strange behavior by a robin

Question
I have a robin who sits on the railing of my deck and continually throws itself at
my dining room window.  This has gone on for at least two days no, I chase it
away, but it only returns in a few minutes.  I worry that the robin is going to hurt
itself or break my window.  Not only is the window extremely dirty but also now
very scratched.  How can I get this robin to move on?  

Answer
Robins are very protective. So if it sees a other robin it will try to scare him away. In the reflection of the window it sees an other robin.
Try bird sounds or images of big scary birds.

Try hanging some before or after the window to take away the reflection.