Doctor T, go back to the first few pages. I have them all broke down into groups there, and the tree ducks are covered.
But yes, they are one of the very few species of waterfowl that really do not like the EXTREME cold. They do just fine in the teens, but subzero and prolonged temps way down there they dont fair so well in.
I have known many Great Lakes area breeders to do very well with them though. They just keep them all in a barn during the worst of the winter.
I've had pretty much all of them, the common ones are the most hardy for sure and best in lower temps, fulvous, wt face, and black belly. The Java from what I have found seem to be the most sensitive to cold, perhaps because they are so tiny. But as long as they have some wind shelter, and you arent below zero a lot they do just fine.