Shallow marshes have 6 inches or less of standing water. Marshes are among the most productive wetlands for birds and mammals. Ducks, geese, wading birds such as herons and egrets, rails, terns, and songbirds make their home in marshes. Raptors, including ospreys, bald eagles, northern harriers, and short-eared owls, hunt and nest in or adjacent to marshes. Muskrats, mink, voles, and mice are common.
Marshes serve as nurseries for young fish.
They also stabilize soil and improve water quality by filtering sediments and absorbing nutrients. The organic matter, called peat, accumulates faster than it decomposes, and open wetlands fill with peat over time. Bogs are specialized, acidic peatlands derived mostly from species of sphagnum moss. Bogs are nutrient poor and generally form in basins with no inlet or outlet for surface water. The lack of fresh water causes the acidity to increase to a level that is toxic to all but specialized plants.