Wing mirror is broken, may have been there a long time... That said, there's a lot of birds in a flock of starlings, so I'd imagine a lot of poo can be deposited very quickly
Once watched a documentary about the Rome starlings, Frightning, that kind of mess on the car is do-able in one nighttime roost.
The person on the sidewalk with the loud speaker, is to scare them off. It is a big problem in Rome.