Bird droppings are REALLY nasty because they just don't leave a residule that can be clayed out but eat into the clearcoat paint. Water droplets also will do the same thing except they act like little magnifying glasses they burn the clear esp if the car is dirty and in the sun. Scratch - X does work well but you have to work at it a few times. The polish is self destructing meaning its really hard to get paint rub through because the polish breaks down while you use it. Had a quarter sized mark on my hood from the car sitting on the dealer's lot for awhile. Had this on delivery - asked them to buff it out - they didn't really make a difference because they were probably scared that they would burn through the clearcoat. SO I did it with some advice from a detailler's forum. Put a small amount on a soft cloth and start rubbing in a circular / figure eight pattern on perimeter of the spot. Look at it with a fluorescent lamp looking sort of sideways. It will start to go away. Essentially you are smoothing out or removing some clearcoat in the process. Just don't go to far - there is a limit before it will go into the base coat even with the Scratch-X. Put on a few coats of wax and it will look fine but if you look in the right light or at the right angle you will see the outline very faintly. Better still is if you run over the area with a random orbital polisher (porter with sponge pad) with some polish then do the wax.