That sucks. I hate the damn birds for doing that. I used to carry wet wipes for those ocasions but as the winter came, they started to freeze, I got a small spray bottle that I keep full with windshield washer fluid and have a box of tissues always in the trunk. I see a bird drip, clean it right up. BTW today I looked how that spot on my dad's car looks and it's still there and I think looks exactly the same. I guess the fuel just shined that part of the trunk and you couldn't see the dropping, oh well.