#1 Acid harm
If you did not know before, droppings contain high levels of acid, which makes them extremely damaging to surfaces they end up sitting on for long periods of time. It is probable that you have seen this happen either on cars that haven’t been cleaned in a long while or, if your parents or grandparents ever had chickens, around the yard or the coop in which they were housed.
The same thing can happen to your home if there are a lot of birds around the property and you cannot reach the space where they have left their droppings. The acid in the droppings can end up decomposing the shingles or even the roof tar, which can lead to moisture seeping into your home. And we all know how hard it is to get rid of mold and moisture once they seep deep into your home.
This is in addition to the foul smell that a lot of these droppings would create on your property.
You may end up having the same problem if you have installed an outdoor bath for our winged friends in our yard. Make sure you clean both the bath and the area around it periodically if you do not want the bird droppings to give you a hard time later.