I birded the Potomac River in Washington County from Shepardstown down to Harpers Ferry stopping at almost all viewing points.  I didn't arrive until 5:15pm and I suspect that may have been too late for the gulls.  I didn't see any gulls on the entire stretch.  The highlights were 3 adult male Common Goldeneyes just south of Shepardstown on Canal Rd.  There were also 8 Double-crested Cormorants and 10 Red-breasted Mergansers here.  I ran into 14 more Red-breasted Mergansers at the mouth of Antietam Creek.  The lighting was too poor at Harpers Ferry to get a good count on the many ducks present.  By this point I was just looking for gull shapes, which there were none.  
 
Matt Hafner
Bel Air, MD