Hawksnest is a showcase for coastal plain ponds

The Coastal Plain Ponds of Cape Cod are mostly deep ponds formed during the last Ice Age by large chunks of ice breaking off the retreating glaciers and causing depressions in the ground called "kettle holes." If the hole was deep enough to reach the water table, then the hole filled with water and became a kettle pond.

Seasonal changes in groundwater level are mirrored by changes in the level of these ponds. The fluctuating water levels alternately flood and expose the shore, and this determines the plant types that can live in these habitats. A rich diversity of wildflowers, grasses, sedges, and rushes inhabit these shorelines, with small, sheltered ponds, and sand/peat soil mixtures having higher diversity. The sandy soils are nutrient poor, so it is not uncommon to find insectivorous plants along the shores.

Global distribution of coastal plain ponds is extremely limited, and therefore so are the plants which grow abundantly on their shores, such as Plymouth gentian (Sabatia kennedyana) and slender arrowhead (Sagittaria teres), which are mostly confined to Plymouth and Barnstable counties. The densest populations of rare species found in Massachusetts are in the Mary Dunn Pond area of Hyannis.

Rare wildlife is also found around coastal plain ponds, occasionally even bald eagles (Haliaeetus leucocephalus), but they avoid ponds surrounded by homes.

Coastal plain ponds are threatened by recreational vehicle traffic, development, littering, water pollution and water table draw-down by nearby municipal wells.

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