The color of the base coat as it gets hotter than other colors and transfers back to the clear and expands it. This allow the acids in the bird dropping to enter the expanded clear.
Who knows what the bird had eaten, that is what makes the acids, of course some birds like a diet of high acid foods.
Then, it got dew, water on it and the day was hot later.
Rule of this in chemistry is for every 16 to 18 degrees F the heat increases above ambient, the chemical compounds present double in activity. The top surfaces(clearcoat) of that blue metallic could have gotten to over 200F.
The acids were carried down into the clear.
Probably had a high ozone day as well, (smog alert, etc) this added another, more active than the oxygen in the water, oxidizer.
Next day, dew or rain on the car, the acids are now really active, so to speak and then the sun came out and heated the acids again.
That will eat paint quicker than anything.
"Just like battery acid on your jeans, no problem until you wash them in warm or hot water."
Ketch
