Decoys can be made more effective for duck hunting with the inexpensive and cheap addition of inexpensive tape. This little accessory can be the final touch that makes your decoy irresistible.
Blue prism tape (available at tackle shops for customizing fishing lures) can be used to make the speculums on your mallard decoys more dazzling.
Paint the whole speculum patch white and then, when the paint dries, apply the tape.
This added touch can make decoy-shy birds come those final few yards.