Inland Open Water

habitat photo
Photo 1 | Photo 2 | Photo 3 | Photo 4 | Photo 5 | Photo 6
Developed shoreline stabilized with riprap on left; undeveloped shoreline on right. Copper Falls State Park, Ashland County. Photo by Aaron Stoltenburg.

Habitat Description

Habitat Crosswalk

Cowardin: Palustrine or lacustrine; littoral; aquatic bed, rooted vascular and floating (Cowardin et al. 1979).
Shaw and Fredine: Type 5: Inland open fresh water (Shaw and Fredine 1971).
Vegetation of Wisconsin: Submergent aquatic community, river and flowage community (Curtis 1971).
WDNR Natural Communities: Submergent Marsh, Submergent Marsh – Oligotrophic, Cold Water Streams, Cool Water Streams, Inland Lakes, Impoundments/Reservoirs, Warm Water Streams, Warm Water Rivers (WDNR 2005).
Wisconsin Wetland Inventory: Open water; aquatic bed, submergent and floating (WDNR 1992).


Inland Open Water comprises all open water habitats in Wisconsin that are not marshes, including lakes, ponds, rivers, and streams. Vegetation here is limited to submergent, floating, and floating-leaved aquatic macrophytes and does not include terrestrial shoreline vegetation (see Wet Prairie, Forested Ridge and Swale, and Forests) or emergent vegetation (see Emergent Marsh and Wild Rice). Floating and floating-leaved macrophytes have leaves on or just under the water’s surface while submergent macrophytes grow up to two meters beneath the surface of the water, although turbid waters may reduce light levels and thus growing conditions to just a few centimeters below the surface. Floating species such as duckweed are supported only by water and thus are sensitive to wind and wave disturbances. Conversely, submergent and floating-leaved plants such as Canadian waterweed and waterlilies are rooted to the substrate, which helps to stabilize bottom sediments and reduce turbidity (Eckblad 1986, Cooke et al. 2005). Submergent and floating macrophytes also perform other vital functions, such as releasing oxygen into the water and providing a surface for important microorganisms that breakdown contaminants and pollutants. Many, especially wild-celery, sago pondweed, and duckweed, also provide important food resources and cover for many species of birds and other wildlife (Wheeler and March 1979, Jahn and Anderson 1986, Kahl 1991, Henderson et al. 1999). Common or characteristic species and genera of Inland Open Water include various species of pondweeds, coon’s-tail, nodding waternymph, American white water-lily, and several species of watermilfoil and bladderwort (WDNR 2005).

Lakes, ponds, rivers, and streams can be extremely diverse in character and aquatic biodiversity. For instance, inland lakes may differ in surrounding landscape, shoreline condition, bottom substrate, history of human settlement and development, productivity, water depth, water chemistry, and size. Streams and rivers are equally diverse resulting from differences in the watershed’s size, topography, land cover, and land use as well as the stream gradient, stream order, bottom substrate, and character of the stream channel (WASAL 2003, WDNR 2005). Despite these varied characteristics, inland open water habitats typically are permanently inundated and often are connected through common water sources such as ground water, precipitation, and surface drainage. Floods also provide seasonal connectivity, both between different components of a watershed and locally between habitat patches (Petts and Calow 1996). Even during normal flow regimes, streams and rivers interact with the adjacent land, upstream reaches and watersheds, flowing watersheds downstream, and people and communities along their course (WASAL 2003, Thompson and Luthin 2004). Because lakes, streams, rivers, and ponds are interconnected parts of larger landscapes, hydrological or ecological alterations at one location may have consequences to the entire watershed. This also factors in restoration efforts since selectively restoring a particular reach of stream or a chemical characteristic of a lake does not guarantee the recovery of the entire aquatic ecosystem (NRC 1992). Therefore, restoration efforts should be coordinated and linked to maintain the dynamic processes of these aquatic systems and improve their ecological function within the landscape (NRC 1992, Alberti et al. 2007).

Historical and Present-day Context and Distribution

Wisconsin has over 15,000 inland lakes, thousands of small ponds totaling 397,000 hectares in surface area, and more than 53,000 kilometers of rivers and streams (WASAL 2003, WDNR 2005). Many of Wisconsin’s lakes and river valleys were formed either by gouging and scraping action of advancing glaciers or as kettle basins during the retreat and ablation of ice during the Pleistocene Ice Ages, which ended approximately 10,000 years ago (Burgis and Morris 1987). The Northern Highlands Ecological Landscape is known for having one of the highest concentrations of kettle lakes in the world (WDNR 2005), but glacial lake beds also are numerous elsewhere in the state, including a series of lakes extending from central Wisconsin to Green Bay and Lake Winnebago and another from Waukesha south to northeastern Illinois. Many of Wisconsin’s rivers such as the Fox, Wolf, Rock, and Upper Wisconsin were influenced by glacial action (Robbins 1991), yet some of our largest river systems are in the unglaciated Driftless Area of southwestern Wisconsin, including the Mississippi, Lower Wisconsin, Lower Chippewa, and Lower Black rivers (E. Epstein, pers. comm.). Manmade lakes and flowages also comprise a significant percentage of inland open water habitats in Wisconsin, sometimes to the ecological detriment of natural waterbodies. Dams, dikes, and other structures used to impound these waters may fragment and impede river processes and consequently cause dramatic ecological changes (see Natural Disturbance and Threats).

Natural Disturbances and Threats

Floods constitute a significant natural disturbance that can influence the physical and biological characteristics of inland open water habitats. The scouring action of flood waters and redistribution of sediments replenishes sandbars in riverine systems and creates new side channels, pools, and other microhabitats. Flood and drought cycles in lake and pond systems also may result in redistribution or re-establishment of emergent aquatic vegetation along shorelines. Despite the ecological benefits of flood events, their capacity to cause considerable economic loss has resulted in elaborate flood control measures. Rivers and streams are frequently channelized, diverted, or impounded for industrial and municipal water supply, irrigation, transportation, hydropower, recreation, waste disposal, and commercial fisheries. Unfortunately, stabilizing the dynamic processes of these aquatic systems often compromises their ecological function and wildlife value. Flood control measures may result in a loss of riparian vegetation and instream cover, altered substrate composition, increased water temperature, and increased bank erosion. Dams may impact habitat quality by blocking migrations of aquatic organisms and altering flow patterns and water quality. Once water flow is obstructed, conditions more closely resemble a closed lake system where soil sediments, excess nutrients, organic matter, toxic substances, and human wastes are trapped and continually recycled. Some of these pollutants may have immediate effects on the composition, structure and function of aquatic communities whereas others may bioaccumulate and concentrate at magnified levels higher in the food chain. For example, lawn fertilizers containing phosphorous can cause rapid changes to an open water plant community. Commonly transported in stormwater runoff, fertilizers may initiate nuisance algal blooms and adversely impact submerged vegetation. On the other hand, impacts of mercury contamination or acidification may not be evident for many years (NRC 1992, Petts and Calow 1996, Henderson et al. 1999, Cooke et al. 2005, Alberti et al. 2007).

Surrounding land use and water-based recreational use also greatly influence the condition and recovery rates of inland open water habitats. Agricultural, logging, and recreational activities such as boating and jet-skiing impact aquatic plant and animal communities by increasing sedimentation and turbidity, reducing overall water quality (NRC 1992), and directly disturbing migrating and nesting birds. Shoreline development may cause soil erosion by wave action or runoff and often removes important habitat components such as coarse woody debris, native grass and shrubs, and emergent and floating vegetation (Woodford and Meyer 2003). These conditions may encourage establishment of invasive plants such as Eurasian water milfoil and curly-leaf pondweed, both of which can outcompete native submergent macrophytes and form monotypic stands with limited wildlife value (Henderson et al. 1999, WDNR 2005). The establishment of carp, zebra mussel, and other exotic species also has had detrimental economic and ecological impacts to Wisconsin’s inland open waters. The interactions between these disturbances and aquatic ecosystems are complex and vary according to site-specific variables. However, any ecological processes that tend to simplify or homogenize aquatic habitats will likely do so to the detriment of open water-associated bird communities (Steen 2006).

Related WBCI Habitats: Great Lakes Open Water, Emergent Marsh, Wild Rice.

Overall Importance of Habitat for Birds

The variety of habitat conditions found within Wisconsin’s inland lakes, ponds, rivers and streams supports a diverse breeding bird community with several state priority species. Belted Kingfisher, Northern Rough-winged Swallow, and Bank Swallow nest in friable soils found along river and stream banks. Mats of floating vegetation provide nesting substrates for priority species such as Redhead, Red-necked Grebe, Forster’s Tern, and Black Tern as well as Pied-billed Grebe, Ruddy Duck, American Coot, and Common Moorhen (Steen 2006, J. March, pers. comm.). Louisiana Waterthrush and Hooded Merganser are commonly found along fast-moving rivers with cobble bottom substrate (Kitchen and Hunt 1969, Cutright 2006). Undeveloped lake shorelines with intact native plant communities and coarse woody debris provide nest sites and escape cover for the Common Loon (Lindsay et al. 2002, Newbrey et al. 2005), while isolated islands in lakes and rivers support colonial waterbirds such as Great Egret, Great Blue Heron, Black-crowned Night Heron and more recently American White Pelican and Double-crested Cormorant (Cutright et al. 2006).

These diverse conditions also supply diverse food resources, including many invertebrates. Large hatches of midges and other aerial insects sometimes attract large concentrations of swallows and swifts. Chironomidae larvae and amphipods are especially important prey items for diving ducks and two exotic invertebrate species – faucet snail and zebra mussel - are increasingly consumed by waterfowl. The faucet snail is most abundant along the Mississippi River near La Crosse and is partially responsible for massive die-offs of American Coot, Lesser Scaup, and other waterfowl species. The snail hosts an intestinal parasite that can prove fatal if ingested. Zebra mussels occur in extremely high densities within the lower Great Lakes and provide an easy food source for many species of diving ducks, particularly Lesser Scaup. In recent years, Lesser Scaup numbers have increased dramatically in areas colonized by zebra mussels. Unfortunately, the apparent benefits of this readily available food source may be negated by the threat of food contamination (i.e., bioaccumulation of toxins; Badzinski and Petrie 2006). Invertebrates inhabiting shorelines of lakes, ponds, rivers, and streams also are important for Solitary Sandpiper, Wilson’s Phalarope, and other migrant shorebirds.

The winter buds and rootstocks of wild-celery, sago pondweed, and other submergent macrophytes provide food for a variety of waterfowl, particularly diving ducks. Large concentrations of Ring-necked Duck, Lesser Scaup, and American Coot, up to fifty percent of the world’s Canvasback population, and twenty percent of the eastern population of Tundra Swan stage along the Upper Mississippi River (UMR) during fall migration as a result of its quality wild-celery beds. Canada Goose, Mallard, Gadwall, Green-winged Teal, American Wigeon, and Common Goldeneye also stage in significant numbers along the UMR pools while its bays, sloughs, and shallow backwaters provide food resources for Great Blue Heron, Great Egret, Wood Duck, and Hooded Merganser (Jahn and Hunt 1964, Jahn and Anderson 1986, USFWS 2006). Because of its importance to staging waterfowl, the Upper Mississippi River National Wildlife and Fish Refuge has limited recreational boating on portions of the refuge during peak migration periods (Kenow et al. 2003).

Inland lakes such as Lakes Winnebago, Poygan, Buttes des Morts, Winneconne, and Koshkonong also provide important migratory staging and feeding areas. Small herons, some shorebirds, and flocks of blackbirds sometimes forage on their floating-leaved aquatic beds. Lakes with a large surface area and high pH may support high abundances of fish and thus piscivorous birds such as Common Merganser, American White Pelican, Bald Eagle, Osprey, Ring-billed Gull (Newbrey et al. 2005) and Horned Grebe (Robbins 1991). Inland lakes such as Big Green Lake and Lake Mendota as well as many river mouths often remain ice-free into January or later and thousands of ducks, geese, swans, grebes, and other waterbirds may occupy these open waters as long as food remains accessible (E. Epstein, J. March, pers. comm.).

Priority Birds

Species Status Habitat and/or Special Habitat Features
Canada Goose
(Mississippi Valley Population)
M, W  
Trumpeter Swan b, m, w Migrant in open waters with extensive beds of sago pondweed and wild-celery.
Tundra Swan M Migrant in open waters with extensive beds of sago pondweed and wild-celery.
American Black Duck b, M, w  
Mallard B, M, W  
Northern Pintail b, m  
Blue-winged Teal B, M  
Canvasback M, w Migrant in open waters with extensive beds of sago pondweed and wild-celery.
Redhead b, m  
Lesser Scaup M Migrant in open waters with abundant amphipod populations.
Hooded Merganser b, M Nests near fast-flowing, gravel-bottomed streams.
Horned Grebe m Migrant on large inland lakes.
Red-necked Grebe b, m Uncommon breeder in open water with mats of submergent vegetation.
Great Egret f Forages in water depths <28cm and along edges of rivers and streams.
Snowy Egret f Forages in water depths <28cm and along edges of rivers and streams.
Osprey B, M Prefers large lakes with high abundance of fish.
Bald Eagle B, M, W Prefers large lakes with high abundance of fish.
Whooping Crane f, m  
Solitary Sandpiper M Forages along banks of wooded lakes, ponds, and streams.
Wilson’s Phalarope b, m  
Forster’s Tern F, m Nests locally in island beds of bulrush, common reed, and cat-tail.
Black Tern F, m  
Belted Kingfisher B, M, W Nests in burrows along stream and river banks.
Northern Rough-winged Swallow B Nests in burrows along stream and river banks.
Bank Swallow B Nests in burrows along stream and river banks.
Louisiana Waterthrush b Nests near fast-flowing, gravel-bottomed streams.


Stay tuned…….will incorporate habitat acreage objectives from Upper Mississippi River and Great Lakes Region Joint Venture Implementation Plan.

Management Recommendations

Landscape-level Recommendations

  1. Improve habitat connectivity and condition by conducting restorations that integrate lake, stream, and wetland components within a watershed.
  2. Maintain aquatic function and biodiversity by minimizing impervious surfaces, limiting loss of wetlands and shoreline habitat, and reducing soil loss and nutrient delivery within watersheds.
  3. Limit development around lakeshores to minimize negative impacts to breeding bird communities (Lindsay et al. 2002).
  4. Encourage wetland management, protection, and restoration efforts on private lands through existing federal and state programs and by educating private landowners on wetland stewardship.
  5. Prevent the introduction of additional exotic species and slow the spread of existing aquatic invasive through improved regulation, education, and management. Such measures are best planned and implemented on a watershed scale.

Site-level Recommendations

  1. To benefit burrow-nesting species such as Bank Swallow, Northern Rough-winged Swallow, and Belted Kingfisher, use “soft-engineering” approaches to bank stabilization and repair rather than “hard engineering” approaches such as dams, levees, channelization, and riprap (NRC 1992).
  2. Remove unneeded dams, dikes, or levees to reestablish hydrological connections between riparian and floodplain habitats and provide a greater variety of successional habitats (NRC 1992).
  3. Convert portions of mowed lawn to native plant species and increase the amount of coarse woody debris along developed shorelines to provide escape cover and habitat complexity (Newbrey et al. 2002, Elias and Meyer 2003).
  4. Work with lake management districts, lake associations, and other natural resource agencies to control carp and other undesirable fish. Use water drawdowns, electrical fish barriers, chemical eradication, and/or physical removal wherever appropriate.
  5. Control nutrient inputs into lakes to prevent the loss of aquatic macrophytes used as forage and cover (Newbrey 2002).
  6. Fence out livestock a minimum of 30 m from the wetland’s edge to protect nesting birds and water quality (Thompson and Luthin 2004).
  7. Minimize disturbances at important nesting and staging areas by instituting voluntary avoidance areas, no-wake or non-motorized zones, fishing and hunting restrictions, and public awareness campaigns during spring and fall migration (Korschgen et al. 1985, Kenow et al. 2003).

Ecological Opportunities

Ecological Landscape Opportunity Management Recommendations
Central Sand Hills Major All
Forest Transition Major All
North Central Forest Major All
Northern Highland Major All
Northwest Sands Major All
Southeast Glacial Plains Major All
Superior Coastal Plain Major All
Western Coulee and Ridges Major All
Western Prairie Major All
Central Lake Michigan Coastal Important All
Central Sand Plains Important All
Northeast Sands Important All
Northern Lake Michigan Coastal Important All
Northwest Lowlands Important All
Southern Lake Michigan Coastal Important All

Research Needs

  1. Implement a marshbird monitoring program to adequately measure abundance, distribution, population status, and habitat use of key species within inland open water habitats. Select focal species that serve as indicators of aquatic ecosystem function and reflect long-term change and response to stress (NRC 1992).
  2. Inventory and protect nest sites for Belted Kingfisher, Northern Rough-winged Swallow, and Bank Swallow. Conduct selective monitoring at key sites to determine factors influencing nest success.
  3. Evaluate agricultural chemicals’ impact on water quality and prey availability within inland open water habitats.
  4. Identify factors affecting food availability at staging areas and assess how these may impact species survival.
  5. Determine shoreline development thresholds for nesting species sensitive to disturbance, including Red-necked Grebe and Common Loon. 
  6. Assess abundance, condition, and trends of inland open water habitats within and across landscapes to prioritize conservation opportunities.
  7. Monitor restoration projects to assess their progression towards planned objectives and provide feedback for future efforts. Restoration objectives should have an ecological rather than economic or recreational basis.


Key Sites

Key Partners

Funding Sources

Information Sources


Contact Information

Kreitinger, K., Y. Steele and A. Paulios, editors. 2013.
The Wisconsin All-bird Conservation Plan, Version 2.0. Wisconsin Bird Conservation Initiative.
Wisconsin Department of Natural Resources. Madison, WI.

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