Wow- I think we were being really over-cautious. It got down in the negs (maybe -5) here w/ windchill. Ducks are in a small shed w/ chickens and a 250 w heatlamp. We added a second 250 w heatlamp and kept everyone in for a few days. Today they are finally outside again for the day (and happy about that!). Even w/ 2 lamps going in an insulated shed, the temp inside got down to 37 degrees.
But, the main reason for keeping everyone inside was to keep the heat in for the chickens (two are not terribly cold hardy). If we open their hatch door, the temp drops in the shed quickly.
We do have a small pond (maybe 7x7 across and 3 ft deep- made w/ those liners) and it is completely frozen and has been since about the beginning of Nov.
To the people who are talking about building a small pond, it is aweful as far as upkeep. The biofilter (that we spent way too much $ for) is no match for ducks, the pump (also big bucks) clogs daily, and the water STINKS! We are trying to figure out another solution for this year. It is a lot of water to drain and refill constantly.
Sharon