Birds, Threats, and Conservation

Site Description
Fairfax, Prince William, Stafford, and King George Counties
Total size: 23,600 hectares = 58,300 acres
Elevation: 0-86 meters = 0-282 feet

The Important Bird Area hugs the south and west shore of the Potomac River from Mathias Point in King George’s County north to Dyke Marsh, just south of Alexandria, Virginia. The river is freshwater and tidal throughout this stretch, including several large tributaries and considerable emergent and forested wetlands. Surrounding uplands have a great deal of topographic relief that supports a diversity of habitat types including grasslands, shrublands, and hardwood forests. Because of the proximity to the Washington DC metropolitan area, there is considerable development pressure from the north and spreading south. There are also many historic properties and landmarks.

One of only two known breeding locations in Virginia for the extinct Bachman’s Warbler was found within the IBA boundaries.

Species at Risk

Bald Eagle: Year-round

• 42 breeding pairs in 2006

• 169 over-summering migrants in 2006

• 288 over-wintering migrants in 2006

King Rail: Breeding Season

• Known to occur annually at Occoquan Bay NWR and periodically at other sites

Least Bittern: Breeding Season

• Frequently encountered at Dyke Marsh and periodically at other sites

Red-headed Woodpecker: Year-round

• Breeding at Huntley Meadows and perhaps other sites

• Wintering and migrating throughout: 37 individuals on 2004 Christmas Bird Counts

Rusty Blackbird: Winter Season

• Wintering in wetlands along the river; 287 individuals on 1999 Christmas Bird Counts

Wood Thrush: Breeding Season

• Common breeder in woodlands, especially in Prince William Forest Park

Worm-eating Warbler: Breeding Season

• Common breeder in woodlands, especially in Prince William Forest Park

Prairie Warbler: Breeding Season

• Prefers open habitats with conifers such as red cedar throughout the IBA

Prothonotary Warbler: Breeding Season

• Prefers wet woodlands throughout the IBA

Louisiana Waterthrush: Breeding Season

• Nests along wooded streams throughout the IBA

Eastern Meadowlark: Year-round

• Declining in open grasslands; 39 individuals on 2004 Christmas Bird Counts

Grasshopper Sparrow: Breeding

• Declining in open grasslands

Field Sparrow: Breeding

• Nests in open shrubby areas throughout the IBA

Congregations

Breeding Colonial Waterbirds: Great Blue Herons and Great Egrets

• 20-30 breeding pairs of Great Blue Herons in 2003

• 20 pairs of Great Egrets in 2003

Wintering Waterfowl: averaging more than 20,000 individuals per year of 25+ species on Christmas Bird Counts (10-year averages in parentheses below)

Tundra Swan, Canada Goose, Wood Duck, American Black Duck (1,445), Mallard, Northern Shoveler, Northern Pintail, Green-winged Teal, Canvasback (1,355), Redhead, Ring-necked Duck, Lesser Scaup (8,640), Bufflehead, Hooded Merganser, Common Merganser (1,400), Ruddy Duck (4,490), and more

Breeding Species Assemblages

Forest Birds: Red-shouldered Hawk, Yellow-billed Cuckoo, Whip-poor-will, Red-headed Woodpecker, Eastern Wood Pewee, Wood Thrush, Prothonotary Warbler, Kentucky Warbler, Hooded Warbler, Worm-eating Warbler, Summer Tanager, and more

Shrub Birds: Northern Bobwhite (may be extirpated from the IBA), Eastern Kingbird, Brown Thrasher, Prairie Warbler, Field Sparrow, Indigo Bunting, Blue Grosbeak, Eastern Towhee, and more

Conservation and Threats

The dominant threat to wildlife within the IBA is the loss of habitat due to urban expansion spreading southward from the Washington DC metropolitan area. Neighboring jurisdictions are experiencing some of the fastest growth rates in the nation. This population increase has led to an increase in recreational boating, which creates disturbances that appear to limit Bald Eagle use of the area. Rapid development of the area will elevate the importance of the protected areas for the management of sensitive species. In addition, improved management of private properties can contribute to wildlife conservation, through such programs as Audubon at Home.

Invasive plant species are a major threat in all habitats of the IBA. Fairfax County lists the following ten plants as the top threats in local forests:

1. Japanese Honeysuckle

2. Stiltgrass

3. Asian Wisteria

4. Tree of Heaven

5. Porcelain Berry

6. Garlic Mustard

7. Chinese Lespedeza

8. Mimosa or Silk Tree

9. Mile-a-Minute or Devil's Tear Thumb

10. Norway Maple

Coordinated action within the IBA on public and private lands could reduce the damage caused by these and other invasive plants. Action should include the planting of native species to replace the invasives.

The IBA includes several important populations of shrub and grassland bird species. However, without intervention, these habitats and their dependent bird populations are lost to forest succession. Active removal of woody plants is required in strategic areas. Occoquan Bay National Wildlife Refuge did a valuable woody-plant-removal project in 2018.

Water quality is a major problem in this stretch of the Potomac River. Improved water treatment by the District of Columbia and Alexandria are the major actions to improve water quality.

For more information about this IBA or to volunteer to contribute information or conservation action, contact us.