Monroe,
 
I agree with JB, the mystery bird appears to be a Virginia Rail.  I  had one 
there as a migrant in May and I presume this would be a migrant as  well.  
Excellent sighting!  Jim Stasz and I were there this evening  and only had Lesser 
Yellowlegs and 1 Semi Plover.  No egrets either.   We actually had very few 
Mallards, most of the ducks were Blue-winged and  Green-winged Teal.  
 
Good birding,
 
Matt Hafner
Bel Air, MD