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 www.nps.gov/gwmp.

Plants Shaped by Water

Turtlehead

“Water is essential for all life,” explained Charles Smith, opening his talk on November 10, 2020, a presentation titled “Plants Shaped by Water.” No matter where plants are, they need water, from a little carnivorous sundew to wetland pickerelweed to giant oak trees.  Some systems, like saltwater and freshwater wetlands, are defined by water.  Smith is a branch chief with the Fairfax County Stormwater Planning Division, a certified ecological restoration practitioner and a Virginia master naturalist instructor. 

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Sora Heard in the Marsh

Sora

The sora (Porzana Carolina) is the most abundant and widely distributed species of marsh-loving birds called rails (family Rallidae) in North America.  In the 1960s, they were frequently seen in migration at Dyke Marsh, according to surveys conducted by Jackson Abbott.

Today, they are rarely encountered, so it was a rare treat when people heard at least five in the marsh in the early morning hours of October 18, 2020.  “The sora makes its presence known with plaintive whistles and whinnies,” wrote Kenn Kaufman in Lives of North American Birds.  This rail is mottled brown and gray with white-edged feathers, around eight to ten inches in length, two to four ounces in weight, has a bright yellow “candy corn”  bill and nervously flicks its tail.

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Dyke Marsh Volunteers Survey Insects

Black swallowtail butterfly

Since 2016, volunteers from FODM and the Audubon Society of Northern Virginia have conducted surveys of butterflies, dragonflies and damselflies in Dyke Marsh from April to October. Here are the total numbers of species documented from 2016 through September 23, 2020: butterflies, 50 species; damselflies, 12 species; dragonflies, 37 species. While surveying, they also document other insects.

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Pandemic Pollution: More Trash

trash bags

Friends of Dyke Marsh volunteers typically collect 30 bags of trash along the Potomac River shoreline during two-hour cleanups. On September 26, 2020, 17 volunteers filled 42 bags.

One consequence of the coronavirus pandemic in 2020 has been a substantial increase the amount of trash on our streets, parking lots and land, much of which ultimately ends up in our waterways.  Observers often find wipes, masks and rubber gloves littered across the landscape.  With more people ordering takeout food, there appears to be an increase in food packaging materials as well.

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Wetland Systems and their Value: Subject of FODM Meeting

Dyke Marsh

At FODM’s quarterly meeting on September 8, 2020, George Mason University professor Dr. Christian Jones gave a Zoom presentation on wetlands systems of the mid-Atlantic region, their value and threats.  Dr. Jones, a freshwater ecologist with GMU’s Potomac Environmental Research and Education Center, explained that wetlands have several valuable functions, including storing water, recharging groundwater, mitigating flooding and buffering shorelines from storms.  Wetlands, like peat bogs, store carbon emitted into the air and thus help mitigate climate change.

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New Dragonfly Species for Dyke Marsh Documented

Swift River dragonfly

On August 19, 2020, Ed Eder identified a dragonfly species in Dyke Marsh, the Swift River cruiser (Macromia illinoiensis illinoiensis), never before documented in the preserve.
These dragonflies are about three inches long and have bright green eyes and a single yellow thoracic side stripe. They have yellow spots along the length of their abdomens. Males have a slightly clubbed tail.

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Marsh Wrens, a Glimmer of Hope?

Marsh wren

In early August 2020, FODMers observed two or three male marsh wrens (Cistothorus palustris) in Dyke Marsh in what FODMers call “the Big Gut.” It appeared that none of the birds had a mate and since it was so late in the breeding season, the observers believe that it will be unlikely for these birds to attract a mate this year so late in the season. 

These volunteers heard the unmistakable bubbly call of the marsh wren and saw several dummy nests but no complete nest. This male likely represents the remnant population of what was once a thriving marsh wren colony and is a reminder of the fragility of the habitat and the loss of significant marsh acreage in the preserve.  See “Restoration.”

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Dyke Marsh Is Lush in the Summer

Dyke Marsh in summer

Dyke Marsh is like a “sea of green” in the summer when wetland plants like wild rice (Zizania aquatica) are at their height.  Wild rice shimmers in the breeze and can grow to be 10 feet tall.  In the second photo, it is in flower or bud. In the third, it is in fruit.

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Saving Our Native Plant Site

Mara Surovell

In partnership with the National Park Service, FODMers have been working in the summer of 2020 to control invasive plants in the .065-acre native plant area.  Volunteers have hauled out bags of plants like mile-a-minute (Persicaria perfoliata), Japanese stiltgrass (Microstegium vimineum), English ivy (Hedera helix) and porcelain berry (Ampelopsis brevipedunculata). 

Invasive plants can outcompete natives and compromise the habitat, so it is important to try to keep them under control.  Many native insects and other wildlife depend on the plants with which they co-evolved.

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FODMer Has Two Photos in Virginia Wildlife

Blue-gray gnatcatchers

FODMer Jane Gamble had two photographs in Virginia Wildlife magazine’s July/August 2020 annual photography showcase which highlighted images from 111 photographers.  One photo was of three blue-gray gnatcatcher nestlings begging for food. The second was a white-tailed doe deer with her fawn.  The magazine is published by the Virginia Department of Wildlife Resources.  Congratulations, Jane.

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Comet Viewed from Dyke Marsh

comet

FODMer Ed Eder snapped a photo of the newly-discovered comet, C/2020 NEOWISE on July 13 at 4:40 a.m.  Ed was looking from Dyke Marsh north-northeast toward the middle of the Woodrow Wilson Bridge and up about 10 degrees.  Ed suggests that after July 15, people should watch for it in the north-northwest sky at night about 80 minutes after sunset. 

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Studying the Habitat Quality of an Area Stream

David Barbour

On June 26, 2020, four FODM volunteers and one Westgrove P.A.C.K. volunteer conducted habitat quality testing in an unnamed intermittent stream flowing through Mount Vernon Park into west Dyke Marsh.  This effort was led by Dan Schwartz and Ashley Palmer of the Northern Virginia Soil and Water Conservation District (NVSWCD).

From 9:30 a.m. to 12 noon, the group took 20 samples from the stream within a 100-meter span, with the goal of identifying 100 living benthic macroinvertebrates.  They found these species:  13 scuds, three trueflies, one aquatic worm and one “other.” 

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