Mason Neck National Wildlife Refuge

Site Description

  • State: Virginia
  • County: Fairfax
  • Ownership: Federal


  • Little Marsh: 58 acres
  • Little Marsh Road: 2 acres

Ecology and Management

Elizabeth Hartwell Mason Neck National Wildlife Refuge (NWR) is part of the Potomac River NWR Complex in northern Virginia, 14 miles from Washington, D.C. It was established in 1969 as the first NWR specifically created to protect an endangered species, the Bald Eagle. The main impoundment on the site (Little Marsh) still frequently hosts foraging Bald Eagles, as well as other fish-eating species (Weller 2011). Little Marsh also contains one of the largest Great Blue Heron rookeries in Virginia. Other breeding species include Least Bittern, Black-crowned Night-heron, Wood Duck and Hooded Merganser. Water level management includes drawing levels down as low as possible in June and July to improve foraging conditions for young Bald Eagles and Great Blue Herons. Sedimentation and encroachment of woody vegetation have been recurring management challenges in the impoundments.


In the past, large storms have overtopped the dike threatening to damage or wash it out.”
-(Weller 2011)

The Little Marsh and Little Marsh Road impoundments both occur on a tidal river (the Potomac), but as they are both essentially dammed tributaries, they may be most susceptible to overtopping due to flooding during large rainfall events.

Human Value

Mason Neck Refuge is located within driving distance of approximately 10 million residents of Virginia, Maryland, and Washington, D.C.
– (Weller 2011)

Approximately 19,000 people per year visit Mason Neck NWR, but foot and boat access is currently prohibited at both impoundments to avoid disturbing sensitive species.

Literature Resources

Below is a list of articles describing research occurring at or near the impoundments:
  • Iwanowicz, L., V. Blazer, A. Pinkney, C. Guy, A. Major, K. Munney, S. Mierzykowski, S. Lingenfelser, A. Secord, and K. Patnode. 2016. Evidence of estrogenic endocrine disruption in smallmouth and largemouth bass inhabiting Northeast US national wildlife refuge waters: A reconnaissance study. Ecotoxicology and environmental safety 124:50-59.
  • Johnson, K. N., A. E. Pinkney, M. J. Melancon, and D. J. Hoffman. Investigation of biochemical indicators of contaminant exposure in great blue herons (Ardea herodias) from Mason Neck NWR. Annapolis, Maryland: U.S. Fish and Wildlife Service, Chesapeake Bay Field Office; 2001. Report nr CBFO-C01-02.
  • Jones, G. S., and M. K. Klimkiewicz. 1971. Mammals of Mason Neck. Atlantic Naturalist 26:108-114.
  • Klimkiewicz, M. K. 1970. Autumn Migration Flyway One Mason-Neck. Atlantic Naturalist 25:160-164.
  • Orr, J., and L. Mendoza. 2011. Herpetofaunal Survey of Mason Neck State Park and Mason Neck National Wildlife Refuge. Catesbeiana 31:59-72.
  • Weller, G. J. Elizabeth Hartwell Mason Neck National Wildlife Refuge and Featherstone National Wildlife Refuge Comprehensive Conservation Plan. Hadley, MA: US Fish and Wildlife Service; 2011.
  • Witt, J. W. 2006. Great Blue Heron productivity at Mason Neck National Wildlife refuge in Northern Virginia, and the potential impacts of weather during a 13-year interval. Waterbirds 29:345-349.