Dave Czaplak alerted me about 3:10 pm of a Black Scoter on the Potomac 
at Violette's Lock.  At 4:05 pm the bird (immature male) was still 
there.  Across from the grassy area along the canal - closer to VA shore 
than to MD.  Dave also had a Commmon Tern (still there as of 4:05) 
sitting on a rock close to VA shore about 150 yds further up river and a 
Black Tern which disapeared upriver before I got there.

Andy Martin
Gaithersburg