How do I get a Cardinal to stay off my cars and away from my windows?

We have had a cardinal "attacking" the mirror on one of our cars and pooping all over it. Then he is sitting on top of my brand new car making a mess on it. He has now started to run into our screen door and also making a mess there. I have tried a mirror from the tree and some sparkling thing to deter him but he has not stopped. What can I do to deter anymore pooping? I love having him fly around and sing but he is messing up our cars.