My flock gave every one of their favorite treats the stinkeye when they first encountered it. They'll eventually figure it out. 'Pecking' at the treat with your fingers seems to trigger them, as well as dipping their beaks in the treat.
Before you know it, you'll have a flock parading around after you when you go outside, just in case you magically produce treats.
Before you know it, you'll have a flock parading around after you when you go outside, just in case you magically produce treats.