Nighthawk

n. A recurring thought that only seems to strike you late at night--an overdue task, a nagging guilt, a looming future--which you sometimes manage to forget for weeks, only to feel it land on your shoulder once again, quietly building a nest. Nighthawks is a famous painting by Edward Hopper, depicting a lonely corner diner late at night. In logging, a nighthawk is a metal ball that slid up and down a riverboat's flagpole, to aid pilots in navigation.