Another +1 to ONR at QD strength.
Soak the dropping with the solution until it is soft and liquefied. For PITA droppings, in addition to soaking the dropping, soak a MF with the solution and set it on top of the affected area (adding a few more shots of ONR QD between the MF and dropping).
Make sure to dab the dropping when removing, don't wipe (as Bigpoppa3346 and Accumulator noted). 90% of bird species ingest sand and gravel to aid in digestion so the sand and gravel is in the dropping and will mar the finish if wiped.
That being said, I've had some droppings that have been on my finish for less than 30 minutes and etched the finish. Other droppings have been on the finish for a couple hours with no damage. A lot has to do with the species and diet of the bird that bombed your finish. The good news is that the droppings that etched my finish were able to removed with a good polish after a few months.
Hope this helps.