Always remove it asap as people have stated. I'm guessing the products were freshly applied prior? A wax or sealant 'should' protect against bird droppings until you have chance to remove it, as long as the products have cured, which vary from one to the next....
I know it seems a faff about, but if your not going to wash the car, the safest way to remove it safely if it has dried is get either kitchen roll or toilet roll, wet it and just place it on top of it, after spraying a little all purpose cleaner or shampoo solution on it, to loosen it for how ever long it takes, wetting it again, as and when. Then pour water over the area to rinse it off, don't scrub at it, as you will scratch your paint...