Marsh Edge Trail at
Blackwater National Wildlife Refuge:
This 1/3-mile walking trail leads from a mature pine forest
to a typical
Eastern Shore marsh of three-square bulrush. Within this area is
a transition zone where the forest and marsh overlap, called an "edge".
Edge habitat has a high diversity of plants, providing important food
and
cover for wildlife. 
During your leisurely half-hour walk, take the time to
observe the abundant
plant and animal life of the marsh ecosystem, one of the most
productive
habitats on Earth. Consider the adaptations plants make to survive
in their environment and think about the value of these plants to
wildlife.
To make your walk more pleasant, please remember that from
April to October, poison ivy is common along the trail. Although
the young leaf buds and white berries are valuable food for birds,
rabbits
and deer, the plant's oils can cause a red, itchy rash in humans.
Remember the saying, "leaves of three, let it be."
Biting insects are present from mid-April through late
September.
Protective clothing and insect repellent are recommended.
1) Loblolly Pines for Endangered Species
Blackwater's forests are mostly loblolly pines mixed with
small
stands of oak. The Eastern Shore is the northern limit of the loblolly
pine's range. Loblollies can be identified by their long, twisted,
yellowish-green needles growing in bundles of three.
Seeds of the loblolly are an important food source for the
refuge's
endangered Delmarva Fox Squirrel. About 550-600 of these large,
light-gray
squirrels live at Blackwater Refuge, one of the largest concentrations
anywhere.
Loblolly pines also serve as perches and nesting sites for
endangered
bald eagles.
2) Shrubs for Wildlife
Many wildlife species depend upon shrubs that grow along the
Marsh Edge
Trail for food and protection. Because it can tolerate semi-saturated
soils, the wax myrtle or northern
bayberry grows close to the marsh edge.
The shiny, yellow-green leaves of wax myrtles are retained
through-out
the winter, and are used in cooking for bay-like seasonings. Birds
feed on wax myrtle berries when other food supplies are depleted, and
the
scented wax from the berries can be used to make candles and soap.
3) Decaying Logs Mean New Life
Under the logs that line the trail you can see the important
process
of decay. As the wood breaks down, it forms a rich organic material
which becomes part of the soil. In the marsh, plants break down into
tiny particles called detritus.
This material is an important food source for shellfish, aquatic
larvae,
and other invertebrates.
4) The Changing Transition Zone
The marsh edge is a transition zone where forest and marsh
meet.
Here, the types of plants change from dry to wet ground, depending on
how
well they can tolerate water. Look for shrubs like groundsel and
wax myrtle in the upper edge of the transition zone.
In the lower edges, cattails and three-square bulrushes grow.
Habitats and vegetation in the transition zone are constantly
changing.
Dead trees along the marsh edges mark where rising water levels changed
woods to marsh.
5) Osprey Nesting Platforms Help Re-establish Populations
In mid-March the osprey returns to the Chesapeake Bay area to
nest.
To help this species, once threatened by DDT, refuge managers have
erected
nesting platforms to increase reproduction. Young ospreys, which
hatch in May, will accompany their parents to South American wintering
grounds in September.
DDT, which caused eggshells to be thin, has been banned in
the
United States since 1972, and no longer threatens osprey populations.
However, it remains a reminder of how humans impact our wildlife and
environment.
6) Greenbriar's Many Uses
A woody vine called common greenbriar serves many purposes
for wildlife
at Blackwater. White-tailed deer feed on its leaves and songbirds
enjoy the dark blue berries. Birds, rabbits and other small rodents
use the dense thicket for protective cover.
7) Bald Eagles Like Isolation
Unlike ospreys, bald eagles cannot tolerate the presence of
people.
Eagles prefer isolated marsh areas bordered by woods for resting and
nesting.
If you look across the marsh, you can see Barbados Island,
where
a pair of eagles have been nesting since 1975.
Isolated islands of loblolly pines like these provide secure
nesting
sites near the abundant food source of the marsh, where eagles can feed
on fish, birds, and other wildlife.
The lands surrounding Blackwater host one of the largest
concentrations
of nesting bald eagles along the Atlantic Coast. An average of
55-60
eagles use the refuge year-round.
8) Olney Three-Square Makes a Good Meal
Olney three-square dominates the marsh at Blackwater,
blooming from
June into September. Look for this three-sided grasslike plant along
the marsh edge towards the boardwalk. The tubers of three-square
are an important food source for ducks, geese, muskrat and nutria.
Waterfowl also feed on the seeds. Bulrush leaves are used by
the
muskrats for building their lodges, and the densely growing stands
serve
as protective cover for nesting songbirds and ducks.
9) The Chesapeake Bay
The Marsh Edge Trail boardwalk borders the Little Blackwater
River which
flows into the Blackwater River near the refuge Observation Tower.
The water then flows into Fishing Bay, an arm of the Chesapeake Bay.
From the boardwalk, try to envision the tides carrying rich
nutrients
and detritus from the marsh to the estuary, an area where fresh and
salt
water mix. This process helps to nourish extensive populations of
microorganisms, fish, crabs, oysters, and clams.
Many types of fish and shellfish use the marsh as a nursery,
because
it offers protective vegetation and rich nutrients to feed their young.
Wetlands like this one are vital to the health of the rivers and Bay;
they
serve as a filter for pollutants and sediments from groundwater and
surface
run off from the land.
10) The Disappearing Marsh
Much of the open water area you see before you was once dense
marsh.
More than 5,000 acres of marsh vegetation have been lost since the
refuge
was established in 1933. Some reasons for this loss include: natural
forces such as the rising sea level, wind and wave erosion, high water
salinity during droughts, and changes in the flow of the Blackwater and
Little Blackwater Rivers.
Outside of the refuge, dredging and filling associated with
development
destroys thousands of acres of marsh each year. Saving existing
wetlands
is the key to restoring the Chesapeake Bay. You can help by encouraging
alternatives to development around the Bay, and by reportingg illegal
dredging
and filling activities in wetland areas.
Some Closing Thoughts
On your walk today, you have experienced the mature loblolly
pine and
three-square marsh habitats of the Eastern Shore. The wildlife that
so many people appreciate depend on these habitats for food, shelter,
nesting
and raising young. These habitats are all integrated ecosystems where
all components are interdependent.
As you consider the future of natural areas and its wildlife,
please
remember how sensitive the natural world is to any changes in the
fragile
balance.
