This is April in front, who is soft and snowy with new plumage.
Ducks didn't molt; when should ducks molt?
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Well according to this article http://greenwing.org/teachersguide/summer01/summer01moreabt.html
ducks are supposed to molt twice a year. Apparently they molt very quickly, could you have missed the molt. But maybe genetics comes into play. I wouldn't worry about it.