I always heard that bird poop will stain your paint's finish, but never saw it first hand...until this past weekend. I don't know if these birds where having a contest or what, but in the 20 minutes it was parked, I had FOUR huge piles on my car (two on the windshield, two on the hood). Holy cow did it wreak havoc on my finish. It took a good 20 minutes of rubbing with Mequire's fine scratch remover (per dropping) to get the "etching" out of the finish.

So the next time this happens to you, don't let it sit (like I did). Remove it ASAP or you'll be rubbing and swearing for a long time to get the stain out!