Quote:
it's from over preening, all goldeneyes and bufflehead as well as most all the sea ducks can and will be bad about it, especially in the south.
It's nothing to worry about, just something they do.
Watch your birds close, they will constantly be preening at the breast area, and actually end up plucking it out like that, look at it's location, it's right where their bills will be at when they tilt their heads down to preen the breast. Some can be from fighting I guess, but all I have had that did it were just heavy preeners. It's very common in the seaduck divers, especially in the hottest months here.