I used to have mango trees in my garden in Oz. They fruit around November/December, attracting a veritable armada of fruit bats. Although not black, fruit bat poo is decidedly sticky and if left unattended can set quite hard. Highly recommended for pot holes in the garden path, but particularly difficult to remove from solar panels on the roof.
We solved the problem by removing the mango trees and replacing them with citrus - only to find that not only did the bats love them too, but the green ants found the trees to be a perfect home.
Sometimes you just can't beat nature.