Blackwater National Wildlife Refuge, located 12 miles south of Cambridge, Maryland, was established in 1933 as a refuge for migratory waterfowl. The refuge includes more than 26,000 acres, composed mainly of rich tidal marsh characterized by fluctuating water levels and variable salinity. Other habitat types include freshwater ponds, mixed evergreen and deciduous forests, and small amounts of cropland and managed impoundments that are seasonally flooded for waterfowl use...