And this is truly where all of those factors come together. Ducks settling in these locations do not have to move any farther south unless they either run out of food, or they lose their sources of open water. Remember - the birds know that they must conserve energy all the way through the winter to return north. And there's the rub.
As we sat, freezing on the Patuxent River (famous for stands of wild rice and nice flocks of teal, black ducks, and mallards) last week and wondered where the hell the ducks were, the ducks were still sitting on open water in the Great Lakes. In January. I saw a Weather Channel update that afternoon - open water on all of the Great Lakes. ALL OF THEM. In January.
In fact, I hear there's still open water in parts of the St. Lawrence River, and in fact, that's where a few million ducks are sitting right now. Content to hedge their bets that maybe, just maybe, they won't have to fly any farther south.