sentences:  In the wintering population of Eastern United States, however, they are often associated with steep river valleys, reservoirs, and marshes in inland areas as well as estuarine marshlands, barrier islands, managed wetlands, sounds, and mouths of major river systems in coastal areas.These wetlands are attractive due to a dominance of open vegetation, large concentrations of prey, and the general absence of human disturbance.In the midwestern United States, they are not uncommon during winter near reservoirs and wildlife refuges that provide foraging opportunities at waterfowl concentrations.