At least here in the Pittsburgh area, automatic car washes do a KILLING in the winter. And they are on every street corner. There are always long lines at the first hint of sunshine. The many "Laser Wash" car washes in this area have enclosed touchless wash bays where the doors open just so the cars can get in and out, so it stays warm inside.
I had the same issue last Saturday with what appeared to be an entire flock of birds having diarrhea all over my car. It was a 16 degree day so hand washing was out of the question, so I spent my $8 and went through the local Laser Wash. Bird poop all gone! But of course, the clean car didnt last long as it snowed that night and now my car is a nice shade of gray from the salt spray on the roads.
But no bird poop at least. lol