Dyke Marsh is one of the largest remaining freshwater wetlands located on the Virginia side of the Potomac River in Fairfax County. With a total size of 485 acres the wetlands comprises of a wide array of plant and animal life. Visitors can access the preserve via "Haul Road" which is a trail that leads into the marsh. Wildlife present at the preserve include beavers, muskrats, red foxes, brown bats, shrews and gray squirrels. The red winged blackbird and over 300 species of birds can be seen in Dyke Marsh. Expert bird watchers are often seen on bird walks each Sunday. During the fall insects such as crickets, katydids, grasshoppers and cicadas can be heard in joyous chorus. Plant life is also in abundance at Dyke Marsh with over 360 species found. The narrow leafed cattail is the most dominant species with bidens laevis, sagittaria, arrow arum, pickerelweed and northern wild rice all seen at the preserve. Dyke Marsh is monitored by the National Park Service and is open all year round.