Yes, bird poop can be harmful to the paint on your car any time of the year, not just the summer. I had some on my RX8 that damaged the paint within a week. The best way to remove it is by washing the car with a good shampoo using a soft wash mitt.
The best way to protect against it in the first place is to make sure the car has a good wax coat applied at all times. This won't stop the poop from sticking but it will give an extra layer of protection between the acidic poop and the paint.
I can't believe it took so long to get this kind of answer.
Wash your car.
Wash it as often as need be... If you see bird poo on the car and you're feeling lazy wipe it off and wash it another day.
Bottom line,
Wash your car as often as you can. 👍
There are products for touch-ups but the bottom line is to wash your car when you can. If you get bird poo on it just lubricate (water if nothing else) and wipe it away, then wash when you can.
I suggest you look into the "two bucket wash" if you can. 👍
Oh, and avoid parking under trees.
Birds love to hang out in trees.
Easy and simple way to get bird lime (as its called) off your car. Get a piece of kitchen towel/roll and soak it in warm water, lay it over the poop and leave for 3-4 minutes. It will then just wipe off, even the dried out bits, and doesn't scratch the finish at all.
That's how we always did it in dealership and it works a treat.