two male northern shoveler ducks on the river in blackwater national wildlife refuge.

bird wildlife waterbird animal duck ducks water waterfowl winter nature wetland beak shorebird marsh male northern shoveler river blackwater national refuge miagrating nwr migrating maryland's eastern shore cambridge maryland dorchester county freshwater impoundments brackish tidal wetlands open united states fish tea-colored waters peat soil marshes species threatened endangered plants migration beak bird bill fly egg tail flock flight feather flight feathers wing chick aviary incubate nest nestling migration migrate rook roost rookery