I was one of the leaders of the BBC Blackwater trip, but had to leave before the group's late afternoon sightings.  However, while driving home on my own at about 3:30 pm, I saw a Rough-Legged Hawk (adult female) flying 40-50 ft. above a farm field on Egypt Rd., just north of Blackwater NWR.  This was almost certainly not the bird Pete Webb and others saw well south of the Refuge.

                                                  Peter Lev
                                                  Baltimore Bird Club