I assume you are referring to the speculum feathers or the featheres at the shoulder. The steam will help you in this situation. Plumed/plummed refers to the degree that the featheres have reached maturity. Like this; You have a duck that just got done molting (summer plummage) and you have a duck that is in it's courtship colors. There is an extreme difference in the both. The breading plummage has vibrant colors (on a drake) the feathers are at there highest quality such as length and fullness. The best example to this is a drake Mallard in August/September, doesn't always have a green head, and are quite difficult to differentiate between a male and female. Come December/January they look green and full, and there head appears much larger. When you fleshed out your Scaup, did you notice a bunch of pin featheres under the fat as you were defatting the quills? Did you notice black rows of immature feathers at the wing pocket, and at the neck and head? When you find these "pins", that is a good indicator of a poorly plumed/plummed bird. The reason I knew it was an "early bird", is that a Scaup shot in the latter part of the season will look like it has an iridescent black/blue/green/purple head, if it is a later bird, the bar across the breast will be straight, black, and full. Unless you shoot a scaup in the spring, they're very hard to get in perfect plummage, so don't feel bad, but they do get better in December/January. Unfortunately here in Wisconsin, our season ends the first weekend in December, so we don't get perfect birds either. Hope the steam helps you out, and good luck!