Set the trap on open ground where magpies congregate to feed on pasture insects. A call bird is not normally needed. The exception to this rule is when the magpies have no obvious feeding ground. Bait the trap as usual and in another cage (possum cage is ideal) to entice the birds down.
Bait the trap with food for magpies. Try butter, beef dripping, mutton fat, bread, dog roll, cat food or mincemeat experiment with a variety of foods, mirrors or tinfoil can also be used.