Bone, if that is a recent photo, then I don't think it's an immature bird. I think it's just not fully plumed out yet. Northern Shovelers are one of the species of duck that does not get fully plumed out until late in the year, sometimes not until January and February.
Once fully plumed out, they are ranked right up there to a Wood duck as far as beauty goes in my book. They are a gorgeous bird.