Engineers are funny guys with an excellent sense of humor. Well, at least they think so.
It was not enough for humanity to have pigeons shitting everywhere, so superminds from the USA came up with a dove-drone. This operator-controlled creature marks the windshields of parked cars from a container with something visually similar to bird droppings. Moreover, unlike real birds, the drone does this aimingly and very plentifully.
Homemade on the theme "How to take revenge on a neighbor."