In the first year, a duck will go through 3 different plumages....the first feathers they grow are juvenile plumage and look much like a hen pintail, although the tail tips are notched, and there are also differences in the size and shape of the feathers to identify juvenile plumage. Soon after they will molt into basic 1 plumage, then, starting in October-January (depending upon hatch date) they will milt into Alternate 1 Plumage which is when they will look like what you think of with the chocolate head. Then again, after breeding, they'll molt into Basic 2 plumage, and while in Basic 2, will molt their wing feathers for the first time. Because both of the basic plumage drakes are not Basic 1 plumage, they have to be older birds.
Clint