To foil the pigeons who keep eating the food we put out for the smaller birds we bought a stand with three hanging feeders which are too narrow for the pigeons to perch on. The pigeons looked a bit dismayed to start with, studying it hard, trying to land on the perches, but without success. We're not being cruel you understand, we do throw stuff out for the pigeons separately, and they do eat the food that the sparrows and finches, etc, drop.
So all was well.
But - my DH was watching them the other morning and could hardly believe his eyes. A sparrow was on the perch, a pigeon below. The sparrow looked at the pigeon, picked up a seed or a nut, and deliberately dropped it down to him. Not once, but several times.
How clever is that?