let me explain something
Bird poop is, summarized and generalized, the same thing as any other animal group’s poop: the final stage of digestion, the getting rid of the garbage. Remarkably though, bird poop is very different from the poop we all know intimately – mammalian poop – in that it contains two fractions: a black part and a white part.
The reason behind the striking colour scheme is rather simple: birds have combined two digestive aspects into one channel that mammals have separated into two: excretion and defecation. And they have a different mode of excretion.
Here’s the chain of events: an animal eats and the food is being digested. Whatever content can be used is absorbed from within the digestive tract into the blood in the form of molecules. Whatever food content cannot be used is thrown out through defecation. The molecules that were absorbed from the food travel through the body in the blood system and then enter the cells. Here they are used for all sorts of things, e. g. to generate energy, build proteins, whatever. And of course, this means the molecules will be split and changed in many ways. This creates molecular waste products, in particular nitrogenous wastes. And this waste needs to go, pronto.
From the cell into the blood and through a filtering device (the kidneys in mammals, birds, and birders) to the outside world. That’s the clear, transparent pee in mammals. And the white mushy part in bird poop.
Once you understand this, bird poop isn't all that bad. I invite birds to poop on my head, it's scientifically beautiful.