A migratory bird decoy wing assembly for use with a migratory bird decoy includes an elongate shaft extending in a straight line between a first end and an opposite second end and a first flexible flag. The first flexible flag is adapted to be flappingly displaceable relative the elongate shaft. The migratory bird decoy wing assembly also includes an elongate shaft mounting device constructed to removably mount the elongate shaft on a body of the migratory bird decoy so that the elongate shaft extends perpendicular to the surface of the migratory bird decoy body and flapping movement of the first flexible flag produced by wind simulates the movement of a bird flapping its wing.