After a rainstorm maybe. That car doesn't look like it has Texas plates though.
As a parrot owner, I can tell you birds will poop every 15-30 minutes they are awake and are most likely to go right before they take off. It makes sense when you think about it - they are lightening their weight just before they have to sustain it in flight. You can also potty-train birds in a limited way so there are designated places to poop in the home and they can be taught to use those places.
It's usually not that bad, but the parking stalls certainly are.
Why any nitwit would pull into a parking slot that's white instead of black baffles me.