so far i've been lucky, i've always got the bird poo off with minimum lingering time, i always carry some QD spray in the car and agitating the bird poo with that always removes it in one go with no marks (the car is also sealed and waxed - car is still beading well enough whenever it rains, which is a lot right now, but needs redoing soon.)
Where i live we have cherry trees and they are currently bearing little fruits. Some of the folks who have parked beneath them have had their cars re-sprayed in a very patchy manner by the pigeons in a very violent purple/black/white effect...
i never park under a tree unless i absolutely have to. The funny thing is that these folks do nothing about the mess on their cars they just leave them to gather more...
