I know the feeling! I was working on this car, little by little.
Anyway, it sat outside in between sessions. One day I come home to see a few bird bombs. Luckily, most of it was on the back glass, and I hadn`t yet polished the roof or trunk lid.
These suckers were a major pain to remove. I tried ALL the tricks, too. A few applications of Poorboy`s Bird Sh#t remover eventually got it off.
The one in the pic wasn`t quite 3" but the one closer to the roof was (no pic of that one) - and what you see in the pic is already after I started cleaning it up!!