THIS WALK IS FULL.  WAITLIST ONLY.  Half day. Explore the diverse habitats in this one-square-mile refuge at the confluence of the Potomac and Occoquan Rivers in Woodbridge, Virginia. A variety of raptors and migratory warblers, vireos, thrushes, and flycatchers should be present, and rails and bitterns are possibilities. Meet at the parking lot in the center of the refuge at 7:30 a.m. Limit: 16. LEADER: Gerry Hawkins at 571-277-8406 or [email protected] or Emily Huang at [email protected]. Directions: From Maryland, take Rt. 495 south to I-95 south, LEFT Exit 161 (Woodbridge), follow Rt. 1 south, cross the Occoquan River, turn left at the light onto Dawson Beach Rd., and follow this road to the end.