Also try picking up a duck even a duckling at night time when it is cold or is just starting to be cold and you'll be amazed how "very warm" their bodies are... I couldn't believe just how warm they were. ~Julie~
As another post said, ducks aren't that demanding for warmth and shelter. Yes shelter should be made available for them for any weather condition but my ducks prefer to stand, lay and swim in the freezing cold rainy weather. I don't lock them up in a coop at night or during the winter time...