An update. It's been a little over a year since the robin episode. Just within the past couple weeks, the problem returned. This time, both Wifey's car and my truck were getting plastered. This happened on the passenger side of both vehicles only. We park with the front of the vehicles pointed West, so for some reason it looks like birds prefer to crap on the North side of the vehicles around here.
Sunday afternoon I came up the driveway to see our little feathered friend take off from the mirror on Wifey's car. When I parked the truck, I angled it a bit so the passenger side mirrors of both vehicles would be visable from one spot inside the garage. With the garage doors open, I took a position in the garage and pumped up the pellet gun. About two minutes passed, and the bird lamded on Wifey's car on the mirror, then made a short flight to the pickup's toolbox. There he made a number of unsuccessful attempts to fly through the back window. Next, he made a short (and final) flight to the truck's mirror. A squeeze of the trigger, the gun went "PHHHTT", and that particular bird went away.
Can't figure out why it's so attractive for birds to sit on the mirrors and crap all over the car door. Now two years in a row, they singled out our place......................chim