Forested Ridge and Swale

habitat photo
Photo 1 | Photo 2 | Photo 3
Interdunal swale adjacent to conifer-dominated ridge. Photo by Emmet Judziewicz.

Habitat Description

Habitat Crosswalk

Cowardin: N/A (Cowardin et al. 1979).
Shaw and Fredine: N/A (Shaw and Fredine 1971).
Vegetation of Wisconsin: N/A (Curtis 1971).
Wisconsin Department of Natural Resources Natural Communities: Great Lakes Ridge and Swale (WDNR 2005).
Wisconsin Wetland Inventory: N/A (WDNR 1992).


Forested Ridge and Swale is an alternating sequence of narrow sandy ridges and low wetland swales that parallels a lakeshore. Although this complex is composed of habitats described elsewhere (see Forests, Wetlands), their configuration and interconnection in this community complex is distinctive. Forested Ridge and Swale and Great Lakes Beach and Dune constitute a series of successional vegetation zones along Lakes Superior and Michigan shorelines. Forested Ridge and Swale develops inland from open dune systems where wind and wave disturbance is reduced and thus conditions are less dynamic (Kost et al 2007). Pioneer trees are able to colonize otherwise marginal habitats because of the wet conditions afforded by swales. These trees may subsequently facilitate colonization of the upland dune ridges by providing shade, litter accumulation, and perches for birds that disperse seeds of understory plant species (Lichter 1998). Forested ridges closest to shore support xerophytic tree species such as red pine, eastern white pine, jack pine, Hill’s oak, and red oak, although some early-successional sites with high water tables may support cottonwood, balsam poplar, and occasionally northern white-cedar. Those further inland support mixed mesophytic forests of northern hardwoods, hemlock hardwoods, and occasionally a boreal forest association of pine, white spruce, balsam fir, and paper birch (WDNR 2005).

Small streams and groundwater maintain the saturated to inundated conditions of the swales. Depending on water depth, swales can support open water, emergent marsh, sedge meadow, wet prairies, shrub swamp, or forested wetland communities (LMTC 2000, WDNR 2005). Permanently inundated swales with emergent vegetation and open water are more common closer to the lakeshore while shrub-or tree-dominated swales prevail further inland. With increasing distance from the lakeshore, forested wetlands of swamp hardwood, bog conifers, or northern white-cedar prevail in the swales. In more acidic conditions, swales may support leather-leaf, Labrador-tea, bog-laurel, and other bog flora (WDNR 2005, Kost et al. 2007).

Historical and Present-day Context and Distribution

Forested Ridge and Swale complexes formed as postglacial uplift caused Great Lakes water levels to recede. If water levels stabilized for an extended period of time, a beach ridge would form along the lake’s shore. This process repeated as meltwaters rebounded from the glacier’s weight or formed new outlets at lower levels. This created a series of parallel, low sand ridges and swales that were eventually colonized by the unique vegetative communities of today. In Wisconsin, this community complex is more extensive along Lake Michigan than Superior. It is best represented at Point Beach Ridges and Woodland Dunes State Natural Areas (Manitowoc County) and Ridges Sanctuary State Natural Area (Door County) along the Lake Michigan coast and at the mouth of the Bad River on the Lake Superior coast (LMTC 2000, WDNR 2005, LSBP 2006). For additional details on Great Lakes shorelines, please see the Great Lakes Beach and Dune page.

Natural Disturbances and Threats

Forested Ridge and Swale habitats are subject to many of the same natural disturbances described in Great Lakes Beach and Dune, including wind and storm events. Windthrow is especially common in the wet forests of the swales because the loose organic soils and high water tables of this community prevent deep root penetration. Its forested component also makes this community vulnerable to unsustainable logging practices and excessive deer browse. Beavers can alter hydrological regimes in affected swales and cause vegetative succession, such as sedge meadow to emergent marsh. Coastal development and associated road building also can disrupt hydrological conditions and adversely impact swales. Diverse habitats here can host a wide variety of invasive species. Particularly aggressive invasives include garlic mustard, purple loosestrife, narrow-leaved cat-tail, hybrid cat-tail, common reed, reed canary grass, spotted knapweed, common buckthorn, glossy buckthorn, and Eurasian honeysuckles (WDNR 2005, Kost et al. 2007).

Related WBCI Habitats: Great Lakes Beach and Dune, Great Lakes Open Water.

Overall Importance of Habitat for Birds

Varied habitat conditions and geographic location makes Forested Ridge and Swale complexes especially important as migratory stopover sites. Raptor species found foraging in or migrating through forested ridges include Turkey Vulture, Bald Eagle, Northern Harrier, Broad-winged Hawk, Cooper’s Hawk, Sharp-shinned Hawk, Merlin, and Peregrine Falcon. Priority species associated with northern mesic and boreal forests such as Least Flycatcher, Olive-sided Flycatcher, Swainson’s Thrush, Veery, Nashville Warbler, Black-throated Green Warbler, Blackburnian Warbler, Canada Warbler, and Purple Finch also regularly occur in forested ridges. Early-successional species such as Ruffed Grouse, Northern Flicker, Chestnut-sided Warbler, and Mourning Warbler can occur if suitable conditions are present. Generalist species such as Mourning Dove, Blue Jay, American Crow, House Wren, Blue-gray Gnatcatcher (Lake Michigan only), Tree Swallow, Song Sparrow, and American Goldfinch are fairly common to abundant. Swales support equally diverse bird assemblages because dominant vegetation varies greatly within and between sites. Where sedges or emergent marsh vegetation dominates, priority species such as American Bittern, Belted Kingfisher, Sedge Wren, Common Yellowthroat, and Swamp Sparrow can occur. Swales dominated by shrubs can support Black-billed Cuckoo, Willow Flycatcher, and Rusty Blackbird (the latter during migration only). Although many of these species are present during the breeding season, their breeding status in this community complex is not well documented (Matteson 1996, WDNR 2005).

Priority Birds

Species Status Habitat and/or Special Habitat Features
Ruffed Grouse b, w Conifer swamp and alder thicket swales; ridges with xeric and mesic forests.
Bald Eagle b, m Nests in tall conifers (white pine) on ridges.
Northern Harrier m Forages over open swales.
Peregrine Falcon m  
American Bittern f, m Occurs in stands of sedges and emergent marsh.
Black-billed Cuckoo b, m Occurs in shrub swamp swales.
Belted Kingfisher f, m Prefers swales adjacent or contiguous to streams, creeks, and lagoons.
Northern Flicker B, M Prefers areas with snags and xeric openings.
Olive-sided Flycatcher b, m  
Willow Flycatcher b, m Occurs in shrub swamp swales, especially bordering openings.
Least Flycatcher b, m Found mostly in ridges forested with hardwood species.
Northern Rough-winged Swallow f, m  
Bank Swallow f, m  
Barn Swallow f, m Forages over open swales.
Sedge Wren b, m Occurs in swales dominated by sedges.
Veery b, m Conifer swamp, hardwood swamp, shrub swamp swales with dense understory.
Nashville Warbler B, M Occurs in semi-open swamp conifer swales.
Chestnut-sided Warbler B, M Occurs in forested ridges with early-successional growth.
Black-throated Green Warbler b, m Prefers forested ridges with mature coniferous, mixed, and deciduous stands.
Blackburnian Warbler b, m Prefers forested ridges with mature pine, hemlock, and spruce stands.
Mourning Warbler b, m Occurs in forested ridges with dense shrub understory.
Common Yellowthroat B, M Prefers swales with tall, rank herbaceous cover.
Canada Warbler b, m Prefers forests with patches of dense undergrowth (e.g., shrubs, ferns).
Swamp Sparrow b, m Prefers swales with tall, rank herbaceous cover.
Rusty Blackbird m Occurs in shrub swamp and hardwood swamp complexes.
Purple Finch b, m Prefers coniferous swamps.


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. Develop a coastal shore and upland habitat conservation program to coordinate funding for conservation projects (GLRC 2005).
  2. Educate the public and stakeholders on the importance and fragility of coastal habitats and their biota through signage, brochures, and guided informational walks.
  3. Conservation efforts should focus on protecting forested ridge and swale complexes from development and fragmentation, preserving natural hydrology, and controlling invasive species. Manage as diverse complexes that are linked by hydrology, landform, and vegetation mosaic (WDNR 2005, Kost et al. 2007).
  4. Reconnect ridge and swale complexes with surrounding upland forest blocks as well as isolated blocks of other ridge and swale landforms.
  5. Maintain and/or restore surface hydrologic connections and water quality throughout any watershed that may feed the swale network. Protect major groundwater recharge and discharge zones of groundwater-fed swales.

Site-level Recommendations

  1. Management practices within forested ridge and swale habitats should mimic natural disturbance regimes whenever possible (LSBP 2006).
  2. If forest management takes place, apply Best Management Practices to minimize detrimental soil and water impacts. Ridges in this system are formed of lake sand and thus can become unstable and eroded when vegetation is removed (WDNR 2005).
  3. For road crossings within a ridge and swale site, assure or restore aquatic organism passage by constructing culverts or similar permanent structures under road.
  4. Because site conditions vary, develop property-specific plans to control invasive species such as garlic mustard, spotted knapweed, and cat-tail (see
  5. Monitor deer browse levels and lower deer numbers wherever feasible.

Ecological Opportunities

Ecological Landscape Opportunity Management Recommendations
Central Lake Michigan Coastal Major All
Northern Lake Michigan Coastal Major All
Superior Coastal Plain Present All

Research Needs

  1. Implement a marshbird monitoring program to adequately measure abundance, distribution, population status, and habitat use of key species within swale complexes.
  2. Quantify use of ridge and swale complexes as migratory stopover sites.
  3. Investigate the effects of different management regimes such as fire, timber harvest, or passive management on nesting species within forested ridges.
  4. Examine the relationship between aquatic insect emergence from swales and migratory bird phenology and habitat usage.
  5. Continue to support research designed to identify effective biological controls for invasive species (WDNR 2005).
  6. Assess the impacts of adjacent land use (e.g., road building) on hydrology and habitat suitability for priority species.


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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