Thanks all for the great info! Our seven silver Appleyards are experiencing their first winter in Maine, and it's been pretty chilly for the past bit (lows in the high single digits F and not getting above freezing most days).
Our ducks have an elevated (unheated) duckhouse with an attached covered run. We have been prepared to lock them in the duckhouse at night if it got "cold enough," but we have yet to do it, as they seem to prefer at night being under the duckhouse, which is entirely banked with straw bales. They have heaps of straw as bedding in both the duckhouse and underneath, and often the two females who are laying will go up to the duckhouse in the early morning to lay and sit on their nests.
Like the OP, however, we've been trying to determine that magic number for when we lock them in at night. To be honest, I think it's probably warmer underneath the duckhouse than in the duckhouse.
In terms of water, we are only giving them fresh water once a day in a heated bucket with the access limited so they can't swim in it.
At dinner time, we top the bucket off with freshwater and then completely dump, clean and refill it every morning. I'm curious about the "unwaterproofing," as we were looking to give them access to their first true bath in a month on Saturday when the temps are supposed to get to 40 F. Thoughts?
One other question we do have is about food. Since the ground has been covered with snow for the past couple weeks, there have been no foraging opportunities at all. At the same time, they are eating significantly less of their pellet feed and not very much supplemental cracked corn either. They still go nuts for greens (and mealworms, of course), and we're trying to get them to like a soup with split peas, greens, floating pellets, etc. Tonight they showed more interest than before in the soup, but their overall food consumption is down even though it's cold. Any thoughts on that front?
Thanks again for the great information from people so much more knowledgable than us! BYC has been a fantastic resource!!!!