This evening when I was driving to our condo in Cape Elizabeth, I noticed a small flock of birds flying a few dozen feet above the road.    Instinctually I assumed they were pigeons or starling . . . but then I looked again and was thrilled to realize they were Common Nighthawks.  This is a bird one never sees except during migration but their song is not uncommon to nocturnal birders.   Common Nighthawk Song