That is interesting... The primary birds we kill are widgeon, green-wing teal, and pintail. All of them callable on the appropriate whistle, but pintail the least so. Here in central California, the whistle is almost useless until later in the season, when things cool down just a bit. The birds get more and more vocal as the season wears on, and the night before opening morning, it sounds like crickets (where there are thousands of birds on the water), and those same birds in December sound like a whistling chorus. Calling each of these birds is a different experience, and certainly different than calling mallards... Out of all three whistling birds, I would say that widgeon are most like calling mallards in how you play them, and how they work in. Green-wing teal are the most callable, which is why they make up such a large percentage of our limits (also the best eating).