Drake whistles or diver whistles are a nice compliment to your main call that mimics the mallard hen. Drake mallards make a ggrrzzzeeett call, teal a pip, pip call, pintails a trilling prrrrt, prrrrt call. All of these calls can help you have more success but the roll of a drake whistle is largely secondary. Concentrate on a single reed mallard call and a drake/pintail whistle will come in time.
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