in all fairness, yes bird sh!t isnt good, and will eat away at goodness in your pointwork, but it wont exactly corrode straight through your paint and metalwork, lol
last night when i went to the car after work, (yes a parked under a tree) i noticed a black tar like birdsh!t patch on my wing (wtf did the bird eat?) anyway today, sprayed some megs ultimate quik detailer on it, it came straight off, nothing to worry about!!!