Choptank River's Natural History

Choptank River's Natural History. Melting Glaciers created the Chesapeake Bay. The Chesapeake Bay was once the extended valley of the Susquehanna River, which flowed directly into the ocean near the mouth of the bay. The Bay and all its tributaries were once non-tidal freshwater rivers flowing through valleys in the last ice age 15,000 years ago when sea level was more than 300 feet below the present level. As the climate warmed and glaciers melted, sea level rose and the Susquehanna Valley and other tributaries like the Choptank flooded with mixtures of freshwater and seawater., Such flooded valleys are called estuaries where ocean salt water mixes with fresh river water producing some of the most biologically rich habitat in the world. Indeed, the Chesapeake Bay has been called an immense protein factory churning up nutrients to microscopic life that feeds the oysters and crabs, which then feed the fishes and other animals, including humans, that benifit from the ever-changing intermixing of fresh and ocean waters., Seasonal changes in the Chesapeake Bay bring infusions of fresh water and nutrients from the rivers that flow into the Bay. Summer increases evaporation and reduces river flow, making the Bay saltier. In the fall the rich-waters stay warmer far longer providing food and refuge for migratory birds. Some birds, the Mallard Duck and Great Blue Heron, live along the river all year long. But many birds, especially the waterfowl, pass by as they migrate each winter to the south and each summer to the north. Examples include the Canada Goose, Canvasback Duck, and Lesser Scaup. Osprey migrate each winter as far south as South America.