Whether feeding birds in summer is right or wrong, it does cause a problem which seems to be far worse this year, probably brought about by the loss of our two cats, and has occasioned the invention of a new device - in the picture, it's under the white board below the central bird table.
The situation has been exacerbated by the arrival of squadrons of juvenile house sparrows. They're messy eaters, throwing out any grain they don't like, particularly the wheat, to get at the ones they do like, mainly the sunflower seeds and millet. These sparrows have become so aggressive that even the resident chaffinches give way to them. They now lurk around below the feeders, picking up the sparrows' cast-offs.
The traps are a brand called Little Nippers. They've been grimly effective.