I have a half decent polish job on my restored '61. Was enjoying a week of camping near Santa Cruz, CA. On day 5 we woke up to a poking/pecking sound. It didn't last that long and I figured the birds were eating bugs off the roof. Over the next couple of days the number of birds and persistence increased to the point they we're waking us up at 5am and going at it all day!
I don't know if it's a fighting thing or spring time mating thing but it's happened to my car rear view mirrors with these little grey and black birds. And like my car doors, we escaped on day 8 with bird poop all over the place!
I may need to think about some kind of cover!