The little owl and the sparrow hawk plastic decoys are very effective in bringing crows and particularly magpies within range, but keep still when these corvids are about - one small move and they will bank away.
I have shot many using these decoys with an air rifle with the decoy sat on top of a fence, they will come down and sit on the next post to the decoy especially during the nesting and fledgling season..
I brought a two call set. The owl call sounds great but the crow call sounds nothing liek a crow. It's the faullhaber one, and for £22 I expected better.