Bird droppings are a hazard to cars everywhere. The droppings are corrosive to car paint and may leave marks. They are something you should take care of as soon as possible; the longer you wait, the worse the stain will become.
Catch bird droppings as early as possible. The longer you wait, the harder it will be to clean off. If you catch the dropping early, you can put some vinegar on the dropping, let it soak it and dab it off with a soft cloth.
Spray some window cleaner on the droppings if the vinegar isn't working. Again, let it soak in and attempt to dab it off. You may try this several times.
Mix the car wash shampoo with warm water and apply the mixture to the bird droppings if they are hardened on. Attempt to rub the droppings out with a non-scratch sponge.
Check with your local auto product shop about which non-scratch sponge and car shampoo are best for your particular car, finish and paint colour.
Always test chemicals on a small area of the car before going all out to make sure they will not harm the finish.