Paradise Ducks

Hey guys,

Saw something strange today. Two paradise ducks were paired up on the grass today doing their usual bleep/honk sound when they see someone. But what caught my eye was that the male (bleeping as they usually do) had the full characteristics (dark black feathers with the brown streaks) of your common male, but with a white head like a female. I know the difference in what each male and female sound like and the male in this instance was definitely making the male bleep sound. Both were full adult size. Any one else seen this?