While were on the subject of birds.

We have a problem with magpies.

We used to have swallows, house martins etc nesting in one of our barns but this year they did not return due to the presence of a family of magpies nesting in a nearby tree. We have three semi-ferral cats who live in the barn which we keep to control mice, the magpies even fly into the barn and chase the cats off their food and eat it themselves. Hence, thin cats, fat magpies and no other birds in the vicinity.

Any ideas of how to get rid of the magpies and not harm anything else. We would like to avoid poisons, for obvious reasons, and shooting, due to horses, sheep and public footpaths.