Happy Earth Day

So I'm noticing bird doo splashed on my front screen door, unable to figure out how it got there and accumulated because birds can't sit or  fly above the front door because there's a gable-like shelter over it, a "porch roof" I guess it's called, with floodlights installed beneath. Yet one night, bothered because the floodlights hadn't been working correctly, I lifted my eyes and -- surprise! -- saw that barn swallows had started on a nest, mainly mud blended with a little dry grass, and tightly molded to the floodlight, requiring a broomstick to break it up and knock it off. This was the first time such a nest has appeared. There were no eggs in it. Now I think I should have left it there, because the usual summer tenants just above the front door are paper wasps, and if you knock at their nest with a broomstick you'll do it only once.