Bird dropping most likely lightly etched the finish. The only way to remove it is to use a cleaner polish. There are several different options from several different companies. I would recommend picking up so meguiars scratch X. Widely available. I would apply with a foam applicator. If that doesn't work, try it with a microfiber towel, that will give some more bite. May take a few applications, but that should do the trick.
If the Meg's doesn't work for you, try our DyNA Ultimate Cleaner. You probably see a slight halo of where the poop was which is etched into the clearcoat. Depending on how long you left it on will dictate how deep it's penetrated. Thus the importance of wiping bird poop off ASAP, even if you have to use a dirty rag and spit (if that's all you have when you notice the poop on your paint) since it's easier to remove the scratches you put in while removing it than to let it etch the clearcoat which makes it a much harder job to remove. You can use a medium foam pad or a MF with the product.
One word, Menzerna. check out autopia.org
You might want both the intensive polish and final polish. I used it to get all of the car wash marks out of my Black Evo's paint when I bought it. Made it look like new again.
Also, keep a microfiber cloth in your glove box with a little spritzer bottle of instant detailer to take care of these things asap.