Female.
Hejresøen.
I'm pretty sure this is not a pure Tufted Duck, since I've never seen a bird with such a bright and speckled chest before. Will look into it...
Frost has arrived, and the lakes are frozen. Except where ducks maintains an opening. I estimated some 4000 had gathered here this day (less in the photo). Also a fair number of Common Pochards are blended in.