Bird walk, night hike - Saturday, April 9 - Patuxent Research Refuge will hold a bird walk from 8 a.m. to 10 a.m. off Powder Mill Road near Laurel. Participants can bring binoculars and field guides. A night hike in search of wildlife will be held from 7 p.m. to 8:30 p.m. Reservations required. 301-497-5887.