I lucked out today and caught some Barrow's Goldeneye ducks with my lens.  Their world population is about 200,000.  That seems rare to me, in the entire world, but they are not an endangered species.  I didn't know this until I took the picture, but their heads aren't really black.  They are deep purple, and you can see a flash of purple on the cheek of the lead duck.  They dive down and eat mollusks.  They only come here in the winter, and for the rest of the year they will go to some mountain lake in Canada or Alaska.  The rest of the day's pictures can be seen here.