Guano is black, but yeah bird poop (and I guess technically sometimes dog poop) is white. If you’re getting dog poop under your windshields, I gotta ask where you park your car?

Fun fact! The difference between guano and other things line rat poop is that guano is basically dry and then it becomes powdery after a couple hours, so even if you have bats living in a nearby area, it’s not much to deal with.