I've thought about this and if birds really were total assholes they would be shitting on people on purpose. If you could fly, and when it was time to have a shit, don't tell me you wouldn't fly off until you spotted someone you didn't like the look of and then try and dump on their head. Birds on the other hand rarely shit on people's heads and when they do the level of incidence is so low, as compared to the shits taking place, that in the vast majority of cases has to be purely accidental.