Update....
I have no trees (don't ask).
There is a nearby evergreen bush and we discovered the nest of babies. The mommy blackbird or whatever it is, I think I had a post last year about them...she takes their poop out of the nest and flies over our pool, like a bomber plane, dropping it next to the owl. Seriously, I think she is aiming for it "Here's more poop, nah nah nah"...
I spend an hour cleaning the pool cover every day since that other post. I wake up, look out side, more bird poop.
Ever go into the bird house at the zoo, where they house the penguins and seabirds...that's how it smells. It's awful. I decided to up my Chlor.
This happens every year, while they are babies. It should end in a few short weeks. Then we have the morning doves that poop on the coping.
We tried my son's cap gun, and the bird didn't even flinch. The only thing that keeps her away is us actually swimming in the pool....