Crow's Nest Natural Area Preserve - Biology of Crow's Nest

Biology of Crow's Nest

Crow's Nest has been referred to as a "biological gem". There have been few formal surveys for rare plant and animal species, however, mostly conducted by the Virginia Department of Conservation and Recreation in the late 1990s.

Virtually the entire 3,000 acres (12 km2) Crow's Nest Peninsula is forested with mature stands of mixed hardwoods. In the words of Gary Fleming, Natural Heritage Program ecologist, "Overall, Crow's Nest supports one of the finest—if not the finest—upland hardwood forests remaining in the Virginia Coastal Plain." Surveys documented two state-listed species and the potential habitat for two other federal listed species and several state-listed species. Several Stafford County records for plants and two state-listed endangered plant species were found, including ginseng (Panax quinquefolius) in rich ravines and river bulrush (Scirpus fluviatilis) in adjacent tidal marshes. Suitable habitat was found for small whorled pogonia (Isotria medeoloides), although it does not grow there.

The peninsula is forested with huge trees, some over 4 feet (1.2 m) in diameter, including chinkapin oak (Quercus muhlenbergii) and tulip poplar (Liriodendron tulipifera). Other trees include bitternut hickory (Carya cordiformis), pignut hickory (Carya glabra), black walnut (Juglans nigra), and black locust (Robinia pseudoacacia).

In addition to the high-quality forests found at Crow's Nest, there are approximately 700 acres (2.8 km2) of freshwater tidal marshes surrounding the peninsula that account for 60% of all marshes in Stafford County. The marshes are in nearly pristine condition and represent some of the best examples found in the state.

Several environmental factors exert important influences on vegetation on the Crow's Nest Peninsula. First, the steep terrain made most of the site unsuitable for agriculture, so it was never fragmented or plowed. It is one of the largest unfragmented patches of hardwood forests in Virginia's coastal plain, in fact. The steepness also limited logging to a substantial degree. Secondly, the mix of freshwater tidal wetlands, ravine bottoms, steep slopes of various aspect, and high ridgecrests has led to a high biodiversity, including sites important in neotropical bird migration. Lastly, the Lower Tertiary deposits in this part of the mid-Atlantic Coastal Plain consist largely of glauconitic sand, shelly clay-silt, and some sandy limestone and calcium-rich sands. These contribute to the development of relatively basic, nutrient-rich soils. Basic or calcareous soil environments are uncommon to rare on the Virginia coastal plain and can support vegetation unusual for the region.

Crow's Nest is surrounded on three sides by a freshwater-tidal estuary, and a multitude of resident and spawning fish thrive in these waters. Local fishermen captured the shortnose sturgeon (Acipenser brevirostrum), a federally listed endangered fish, twice in 2002.

A variety of marine fossils have been found on the shores of Crow's Nest. These include Paleocene-epoch shark teeth, as well as ancient parts of rays, turtles, and numerous mollusks of genus Turritella. Turritella has an elongated, highly coiled corkscrew shape. The internal molds and casts of these gastropods can be found in these waters and are especially plentiful at nearby Bull Bluff on Potomac Creek.

Many of the calcareous ravine forests on the east coast of the United States have been logged, and the Virginia Department of Conservation listed this ecosystem as a conservation priority. The Crow's Nest site is one of Virginia's best remaining examples of this rare habitat and associated vegetation types. These communities are rare in the coastal plain ecosystem. The principal rich forest associated with ravines down-cutting into lime sands and localized shell concretions is currently classified as the Northern Coastal Plain/Piedmont Basic Mesic Hardwood Forest and is found on two dry, very steep slopes facing Potomac Creek.

More study is required for a better understanding of the environment and ecology at Crow's Nest. In the larger context of biodiversity protection in Virginia and the mid-Atlantic region, the factors which contribute to the unique character of this region and its important neotropical migrant populations include its size, large-patch community dynamics, its diversity of habitats, and the known or potential occurrence of rare ecosystems and biota.