Magpies are primarily ground feeders so can you scatter food on the lawn away from the hanging feeders and the bird table. If you scatter bread crumbs and mixed bird seed over the ground the large birds, blackbirds, sparrows, chaffinches, greenfinches, wagtails, yellow hammers etc are happy to feed on the ground leaving the feeders free for tits, goldfinches, siskins and other small birds.
They seem to take it in turns to attend the feeding stations and although Magpies, Jays, Jackdaws, Pigeons, Doves will take the larger bits of food there is always a lot of small pieces left on the ground for the smaller birds.
I currently have a pair of Magpies visiting everyday plus the occasional Jackdaw. Soon the Pigeon and Jays will arrive as the weather gets colder. This does not stop the blackbirds, sparrows, greenfinches, chaffinches, wren, dunnock, robin, starling, tits, nuthatches and goldfinches and soon the siskins and longtailed tits.