Get a Beamann air rifle. Get the .22 cal not the .188. It will penetrate the feathers and still knock it off the vehicle so not to blood spatter the ride. For thos who are interested, its an air/spring rifle and kicks like a .22 but naturally doesn't have the distance.

 

Put something on top of your mirror that it would not want to sit on... for instance, make a U with three boards... Put carpet on the inside to protect your mirror. Drill screws from the inside out and then put it on your mirror so the screws are sticking up. Once it realizes it cannot land there, it wont!