I'm sure in the past I have written many articles about my pet ducks including my favorite girl Doc. Doc is one of my Black Swedish Ducks and she is so beautiful.
Doc and her sister Debbie (pictured below) were like twins when they were born. They had the same exact feathers and black spots in the same spot. If they were moving around I had a hard time tell who was who and I'd have to study them very hard to tell them apart.
Debbie on the Left and Doc on the Right 
Even in this picture you can see Doc's colors changing more white on her lower feathers. Doc is three years old now and starting around the age of one she started shifting from a mostly black duck to a mostly white duck.
It's very interesting how much she changed colors. All of my Black Swedish have changed colors as they age but none quite so much as my beautiful Doc.