The suggestion to fold the mirrors in was a good one and should solve the problem. However, the suggestion to hang a mirror elsewhere may not have been so great, especially when spring comes. Male birds become very territorial in spring and will attack their reflections thinking they’re seeing intruders in their territories. While amusing to watch, this is a waste of their time and energy and can cause them to injure themselves. If the bird happens to be a large woodpecker, the mirror won’t last long.
To Kathy from Cincinatti, try getting a fake owl. They’re available from most home and garden places. They have a scarecrow effect. We used one to keep squirrels away from our bird feeder. It may deter cardinals.
I agree with the other comment. Except try a ceramic cat. Try putting on your dashboard.
Talk about coincidence! When I walked out to my car after listening to the show, there was a bird perched on the driver sideview mirror! Not a Cardinal, but a Saffron Finch (a South American bird that’s been imported here in Hawaii). It could be a mating thing. These birds normally live in pairs so maybe he/she is looking for love. I’ll let it be unless it gets annoying.