Apologies for the late posting--I birded early yesterday afternoon from Great Falls to about a mile upstream along the Riverside Trail.  Almost all the ducks were along the VA side of the river (I did not have a scope with me)
 
Two birds of interest/note--
 
--about a 3/4 of a mile up from the dam I found a very dark with a white spot on its head.  I could not get a view of its bill from my vantage point.  The bird has a similar jizz to a surf scoter but I would not officially call it unless some one can confirm this
 
--around the same point I got a very good look at a good-sized grebe (noticeably larger than a pied billed) with a long neck with almost no color in the neck--not entirely sure what this was
 
Other highlights:  approximately 1,000 ring-necked ducks near the dam with 6 redheads mixed in--very nice sight
3  tundra swans
6 hooded mergansers
2 common mergansers
 
Matt Von Hendy
Rockville