I wondered the same thing and the first thing I thought of was bird poop. I also live in West Virginia and actually my property looks a lot like this. We have a lot of woodpeckers and owls. I have a hard enough time keeping my normal windows clean! Rain may wash away dust and dirt, but the bird doo is a different story. Very beautiful though. I have trees growing through my deck like this and the nuthatches, squirrels, and chipmunks are constantly running up and down them. Would be cool to see that inside the house.