Rosybill Pochards (Netta peposaca) are king of South American ducks.  The drake rosybill is synonymous and inseparable with Argentina duck hunting in my mind.  I first became fascinated with them years before ever Argentina duck hunting, while reading about them, seeing photos duck straps heavy with a morning's take.  My first Argentina sighting many years ago: the red fleshy knobs of the drakes' bills contrasted with onyx-black plumage was instantly recognizable from across the wide lagoon as they raced towards our blind.