Friends of Dyke Marsh is a volunteer group dedicated to preserving, restoring and enhancing Dyke Marsh, a freshwater tidal marsh in Fairfax County on the Potomac River just south of Alexandria, Virginia. The Dyke Marsh Wildlife Preserve is administered by the National Park Service.

What Is Dyke Marsh?

The Dyke Marsh Wildlife Preserve is a freshwater, tidal marsh on the Virginia side of the Potomac River in Fairfax County. It is a unit of the George Washington Memorial Parkway, U.S. National Park Service. For more information, visit the NPS website at

Marsh Wrens, Charming Birds

Dr. Luttrell

“Marsh wrens are special, very charming birds,” Dr. Sarah Luttrell told the Friends of Dyke Marsh on February 25, 2018.   Her presentation focused on how comparing multiple traits, including plumage color, size, shape, vocal behavior and genetics, reveals a pattern of evolution.  “Genetic variations are very high within a marsh,” she said.

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Bald Eagles Make Dyke Marsh their Home

Eagle nest

As of early February 2018, three bald eagle pairs have active nests in the Dyke Marsh Wildlife Preserve.  Observers have seen eagles taking sticks to nests, pairs perched, females incubating eggs and a male taking prey to a female on the nest.  

Bald eagles lay two to three eggs in late winter and females incubate the eggs for five to six weeks.  Between May and July, chicks fledge at 10 to 12 weeks of age.  Nest construction, breeding, nesting and eaglet hatching do not always succeed.

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Mammals Stand Out on an Icy Dyke Marsh

Red fox

The January 2018 cold snap and days of subfreezing temperatures brought out winter’s beauty in Dyke Marsh.   Particularly stunning against the icy white background was a red fox (Vulpes Vulpes), photographed by Ed Eder on January 2 off the boardwalk. The fox was prying a piece of dead fish embedded in the ice as another fox called.  Eventually, the vocalizing fox joined the foraging fox.

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Wintering Waterfowl

snow goose

Waterfowl numbers in Dyke Marsh, Hunting Creek and along the Potomac River multiply in the winter and many people love to study and identify them.  Waterfowl are ducks, geese and swans, birds that require water bodies or aquatic habitats to survive.  These birds have waterproof feathers, webbed feet and broad bills. 

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SAV, Important to the River’s Health

water stargrass

Submerged aquatic vegetation (SAV), native and non-native, is increasing in the Potomac River and helps improve water quality, reported the Interstate Commission on the Potomac River Basin (ICPRB), citing the September 13, 2017, presentation to the Friends of Dyke Marsh by Dr. Nancy Rybicki, U.S. Geological Survey (see below). 

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Hunting Creek, Its Ecology and Health

Hunting Creek

Dr. Kim de Mutsert, Assistant Professor, George Mason University (GMU), gave a presentation to the Friends of Dyke Marsh, the Potomac Riverkeeper and the Northern Virginia Conservation Trust on November 15, 2017, examining the health of Hunting Creek, a tributary of the Potomac River just north of Dyke Marsh.  This stream receives treated wastewater from the Alexandria Renew Enterprises wastewater treatment plant and untreated stormwater runoff.   Since 2013, Alexandria Renew has funded GMU’s Potomac Environmental Research and Education Center to monitor water quality and the biological communities of Hunting Creek.

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Local Teachers Explore Learning Opportunities in Dyke Marsh


Three Mount Vernon High School teachers visited Dyke Marsh on November 19, 2017, doing “advance work” to prepare to bring MVHS environmental science and biology students to Dyke Marsh soon. Linda Townley, Victoria Correa and Amy Niss explored the flora, fauna and habitats of the preserve with NPS ranger Alex Parody, FODMers Ed Eder, Ned Stone and Glenda Booth, and discussed plans for students to visit and learn.

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Saving Dyke Marsh’s Trees


Fifteen enthusiastic volunteers helped rescue trees from invasive plants on a drizzly Sunday morning, November 5, 2017, working in the marsh along the bicycle path across from Tulane Drive.  They tackled English ivy, porcelainberry, clematis/Virgin’s bower, honeysuckle and bittersweet, most of which can threaten the survival of many trees and shrubs.  The trees and shrubs targeted included oaks, hollies, sassafrases, hornbeams, blackhaws, viburnums, spicebushes and strawberry bushes. 

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Volunteers Identify Butterflies and Dragonflies

Eastern tiger swallowtail

In the spring, summer and fall of 2017, a team of volunteers conducted regular surveys of Lepidoptera (butterflies, moths and skippers) and Odonata (dragonflies and damselflies) in the Dyke Marsh Wildlife Preserve.  Here are a few examples of their sightings:  

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Good News on the Treated Pumpkin Ash Trees

ash inspection

Since 2015, working with the National Park Service, FODM has been trying to save some of the pumpkin ash trees (Fraxinus profunda) of the marsh that are being attacked by the invasive, lethal insect, the emerald ash borer (Agrilus planipennis) (See our longer article in “Marsh Life”). 

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New Plant Observed in Dyke Marsh

brown-eyed Susan

Several people observed brown-eyed Susans (Rudbeckia triloba) this summer, 2017, along the Haul Road.  It appears to be a new species of Rudbeckia for Dyke Marsh and this is the first photographic record of the species on George Washington Memorial Parkway (GWMP) properties.  The plant was last observed in GWMP in Great Falls Park in 1919.

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Monarchs Migrate through Dyke Marsh in the Fall


In the fall of 2017, the last generation of eastern monarch butterflies (Danaus plexippus) is migrating  southwest to the mountains of central Mexico.  Some of the butterflies are stopping to sip nectar from the masses of smooth beggartick blossoms blooming in Dyke Marsh.

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