I have never worn a mask either, but it IS possible to get histoplasmosis (sp?), a respiratory fungal infection, from bird or bat droppings. It's very serious. Kind of like toxoplasmosis that you can get from cat litter. That's why they tell pregnant women not to change cat litter boxes -can harm fetus. The histoplasmosis can get you whether your pregnant or not. I had a friend who was sick with it for a long time, but not sure how she acquired it. Didn't own birds, but they were doing yard construction, and tearing up the soil. Scary. Anyway, something to think about, or research if you want.