Hey, stupid! The feeder’s empty!
When I am slow to refill the feeder, birds rummage in the tray and sometimes find a seed among the debris that has accumulated. Then they usually go elsewhere for a while.
Sometimes a chickadee (but never a bird of another species) has a different response. The chickadee sits on the edge of the tray (looking into my house) and glares at me. Corvids and parrots are not the only brainy birds.