habitat photo
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Red oak-white oak forest, Quincy Bluff State Natural Area, Adams County. Photo by Eric Epstein.

Habitat Description

Habitat Crosswalk

Wisconsin Department of Natural Resources Silviculture Handbook: Oak (WDNR 2010).
Kotar Habitat Types: PEu; PVCr; PVG; PVGy; PVHa; PVRh; AArL; AArVb; AFrDe(Vb); AQVb-Gr; ArCi; ArCi-Ph; ArDe; ArDe-V; ATiAs(De); ATiCr(As); ATiCr(O); ATiDe; ATiDe(Pr); ATiDe-As; ATiFrCa(O); ATiFrCi; ATiFrVb; ATiFrVb(Cr); ATiH; ATiSa (Kotar and Burger 1996)
Wisconsin Department of Natural Resources Natural Communities: Southern Dry Forest; Southern Dry-mesic Forest; Oak Woodland (WDNR 2005).
USDA Forest Service, Forest Inventory and Analysis (FIA): Oak/Hickory Group (http://fia.fs.fed.us/).
Vegetation of Wisconsin: Southern Dry Forest; Southern Dry-mesic Forest (Curtis 1959).


This Habitat Page covers the oak forests and woodlands of southern and central Wisconsin (roughly south of the Tension Zone; see Curtis 1959), where oak species comprise 50% or more of the basal area and where total forest canopy is greater than 50% (except in regenerating stands).  This cover type includes the Southern Dry Forest and Southern Dry-mesic Forest natural communities (as well as several others where oak may be dominant or common) and the FIA oak-hickory forest type group.  Dominant species are red oak, white oak, black oak, or bur oak, with shagbark hickory, red maple, aspens, basswood, paper birch, white pine, and black cherry as common associates (WDNR 2011a).  The cover type may occur on a wide variety of dry to mesic sites, with site conditions and land use history influencing species composition and successional pathways.  More detail on this range of variability and geographic distribution of different oak species in Wisconsin may be found in the Oak chapter of the Silviculture and Forest Aesthetics Handbook (WDNR 2011b).

Oak stands on sandy sites tend to be dominated by black, northern pin, and white oaks, while stands on thin soils or dry slopes tend to be dominated by white oak and bur oak.  These droughty but not nutrient-poor hillside sites may have semi-open canopies where light can penetrate to the ground and stimulate growth of relatively dense understory layers, especially where ground fires are absent.  Canopy associates on dry sites can include quaking aspen, white pine, red pine, jack pine, and white birch; dry-mesic associates commonly include bigtooth aspen, black cherry, and red maple.  Typical understory species on dry and dry-mesic sites are hazelnut, gray dogwood, hog-peanut, false Solomon’s seal, lopseed, tick-trefoils, and enchanter’s nightshade.

On moister, richer sites or dry sites that are succeeding to more mesophytic species, the more shade-tolerant red oak often dominates, producing moderate canopy closure.  White oak, black oak, bur oak, hickories, elms, black cherry, black walnut, and bigtooth aspen are common canopy associates on more mesic sites.  Sugar maple often succeeds oaks on these sites if a seed source is present nearby, along with other shade-tolerant species such as white ash, yellowbud hickory, and basswood.  The understory flora can be diverse, with many of the same species as on drier sites but also including species such as jack-in-the-pulpit, large-flowered bellwort, interrupted fern, and lady fern (Mossman and Hoffman 1989; WDNR 2011a, b).

On wet-mesic and wet sites where oak occurs, swamp white oak is the characteristic dominant, although white, black, and bur oaks also may be present; red maple, silver maple, ashes, elms, yellowbud hickory, hackberry, and basswood are common associates.  These sites are covered in the Bottomland/Swamp Hardwood Habitat Page.

The Oak cover type also includes Oak Woodland, a community that has succeeded mostly to forest and is now rare.  It is defined as being intermediate between oak savannas and oak forests, with trees lacking the distinctive ‘open-grown’ limb architecture seen in savannas, greater canopy closure than savannas, ranging from approximately 50% to as much as 95% but often less than most oak forests, and a relatively open understory resulting from frequent low-intensity fires.  White oak, bur oak, and black oak are dominant species, with red oak and shagback hickory sometimes present.  Under a presettlement disturbance regime, shrubs and saplings would have been infrequent.  In contrast, the herb layer could be diverse, with a mix of savanna and forest species including grasses, legumes, composites, and other species adapted to filtered-light conditions.  Typical species include upland boneset, violet bush-clover, Virginia bush-clover, Culver’s-root, rough-leaved sunflower, Eastern shooting-star, Short’s aster, pimpernel, bottlebrush grass, silky wild-rye, and bracted tick-trefoil (WDNR 2008a).

Historical and Present-day Context and Distribution

Although sources agree that oak historically was, and continues to be, widespread in southern Wisconsin, estimates for historic and current acreages of oak-dominated forests vary.  Mossman and Hoffman (1989), using estimates derived from Lindberg and Hoving (1985), give a total presettlement figure of 4.8 million acres for southern Wisconsin upland forests (including the more mesic type dominated by sugar maple and basswood), of which the oak-dominated dry and dry-mesic types comprised 1.4 million acres.  Finley’s (1976) estimates for southern Wisconsin are 4.5 million acres and 3.3 million acres of oak forests and oak opening, respectively, composed primarily of black, white, and bur oaks.  Red, white, and black oaks also were a significant component of northern hardwood (sugar maple-basswood-beech) forests; Finley estimated 2.4 million acres of this type in southern Wisconsin.  Oak forests were most common in the Western Coulee and Ridges Ecological Landscape, and were overall less common in southern Wisconsin than oak savanna, which covered approximately 5.5 million acres (WDNR 2011a).  There is no presettlement estimate for oak woodland, which would have occurred where frequent, low-intensity fires created intermediate canopy closure and an open understory.  In the absence of fire, most of these woodlands evidently have succeeded to what Curtis (1959) described as southern dry and dry-mesic forests (Staffen 2010), and woodland probably was included in his presettlement estimate of 1.4 million acres of these forest communities.  Currently, oak woodland acreage for the entire state is estimated at 140,000 acres (Staffen 2010).

Disturbance events such as wind and particularly fire, both naturally occurring fires and especially those set by Native Americans, were critical factors in the historic distribution, and predominance, of oak.  Periodic fires played an important role in the development and maintenance of oak cover types, with variations in site characteristics and fire intensity and frequency determining structural condition and species composition, ranging from oak forest to woodland to savanna (WDNR 2011b).

With Euro-American settlement, oak forests and woodlands were subjected to widespread clearing for agriculture and for use as building materials and fuels.  The cutting and burning used to clear the land, subsequent farming and pasturing, and then abandonment of land that was marginal for cultivation created conditions favoring oaks over more shade-tolerant, less fire-adapted species.  Today’s oak forests are a result of these post-cutover land management practices, as well as more recent management practices and threats.  Currently, the oak-hickory type is the third most common forest cover type in Wisconsin, occupying 3.4 million acres statewide, some 2.7 million acres of which occur in southern Wisconsin.  However, oak forests have suffered, especially from widespread fire suppression but also from fragmentation, excessive grazing and white-tailed deer herbivory, unsustainable logging, and invasive species.  While oaks still dominate a majority of oak-hickory stands, oak forests throughout southern Wisconsin are steadily succeeding to more shade-tolerant species such as maples, elms, and ashes (WDNR 2011a, b).

Oak-hickory forests in southern Wisconsin are most prevalent in the Western Coulee and Ridges Ecological Landscape and also are common in the Central Sand Hills, Central Sand Plains, and the Southern Kettle Moraine region of the Southeast Glacial Plains.  Other Landscapes with less oak but which support important oak-dominated sites are Central Lake Michigan Coastal, Southern Lake Michigan Coastal, Southwest Savanna, and Western Prairie (WDNR 2011a, 2008 b, c).

Natural Disturbances and Threats

Southern Wisconsin’s oak-dominated communities are part of a vast and diverse array of fire-adapted plant communities that once covered much of the eastern United States.  Fire is the key natural disturbance that historically influenced these communities, although it functioned within a complex, interrelated system of many factors (e.g., topography, soil characteristics, the actions of burrowing and grazing animals, etc.) that together shaped community distribution, structure, and composition (Staffen 2010).

Presettlement oak forests and woodlands in southern Wisconsin likely were maintained by fires of relatively high frequency (5-15 years) and low intensity (flames less than 2 feet in length) which consumed leaf litter and small woody debris.  This would have produced the open and park-like structure, with widely-spaced trees and few shrubs or saplings, commonly noted by early explorers and settlers when describing the oaks of southern Wisconsin.  Higher-intensity fires (flames greater than 2 feet) at longer intervals (>50 years) would have killed overstory trees and allowed more light to reach the forest floor, giving oak regeneration a competitive advantage as a new stand developed (WDNR 2011b).

Oak forests were greatly reduced in extent by the widespread land clearing for agriculture and building materials that followed Euro-American settlement, although some of these practices (burning, grazing) also created suitable conditions for oak regeneration on farmsteads that were marginal for cultivation and abandoned.  However, decades of fire suppression, in combination with other factors, has dramatically affected present-day oak forests.  Oaks are steadily giving way to more shade-tolerant species, most dramatically on mesic sites where soils are ideal for tree growth and fire was the primary factor limiting woody competition.  Excessive herbivory from domestic livestock or overabundant white-tailed deer, and selective logging of the largest, highest-quality, most commercially valuable trees (“high-grading”) have combined with fire suppression to remove oaks and limit oak regeneration on a variety of sites.  Sugar maple, red maple, red elm, white ash, black cherry, and ironwood are replacing oaks due to their greater shade-tolerance, ability to resprout vigorously after logging, more rapid growth rates, and lower palatability to deer and cattle than seedling or sapling oaks.  Declines documented between 1996 and 2004 in the acreage of both young oak-hickory stands and stands older than 100 years reflect these changes and suggest that oak will continue to decline in the future (WDNR 2011 a, b).

Fire suppression also has affected both the woody and herbaceous components of oak forest understories (Rogers et al. 2008).  Shrubs and saplings of shade-tolerant but fire-sensitive species (e.g., prickly-ash, maples), have become much more prevalent.  By contrast, numerous light-demanding plants, including grasses, sedges, legumes, figworts, mints, parsleys, and a variety of composites such as goldenrods, asters, and sunflowers that once were common in southern oak forests have greatly declined.  Now they often occur only in large canopy gaps, edges, or along trails (WDNR 2011a).

Oak forests have been reduced and fragmented by clearing for development, a process which has accelerated in recent decades as human populations have increased.  Rural housing development is an increasing threat to oak forests and woodlands, particularly in the Driftless Area which has experienced considerable housing growth in the past several decades (Radeloff et al. 2005).  This rural sprawl reduces the amount of interior forest, degrades and fragments restorable tracts, and limits management options, especially prescribed fire.  Few large tracts remain in southern Wisconsin, and these tend to be located in areas where development is limited by inaccessibility (e.g., steep topography or susceptibility to flooding), low commercial value, or public land.

Non-native invasive plants are greatly impacting southern oak forests, altering forest structure and composition and ultimately affecting successional patterns and future conditions (Rogers et al. 2008).  The woody shrubs invading oak forests are increasingly likely to be exotics such as buckthorns, honeysuckles, Japanese barberry, and, in stands with a history of agriculture or grazing, multiflora rose and autumn olive.  These shrubs impede regeneration and may affect tree growth rates.  The exotic Oriental bittersweet is a vine that can climb and girdle trees.  Among herbaceous invaders, garlic mustard has arguably the greatest negative impact on native understory plants as it is one of the few species that can proliferate in the shade of a forest understory.  Rapidly spreading throughout much of the state, it readily outcompetes and excludes native herbaceous plants and also has been implicated in impacting tree growth rates (WDNR 2011b).  These exotic invaders are very expensive to control and their spread can be facilitated by many methods including adverse disturbances such as exurban development, fragmentation, or livestock grazing, by management practices such as timber harvest, and by human foot traffic and the movement of wildlife.

Native invaders can pose similar problems in some areas; for example, red cedars on unburned, thin-soiled savannas or prickly ash in unburned sites, especially after grazing.

Oaks also are affected by an introduced insect, the gyspy moth, which is well-established in Wisconsin, particularly the eastern half of the state, with records from nearly every county.  Gypsy moths periodically increase to very high numbers and cause significant defoliation.  Oaks are favored hosts of gypsy moth larvae and often sustain more damage than less favored species such as maples.  Outbreaks can occur as frequently as every 5 years in dry, oak-dominated forests (WDNR 2011b).

The replacement of fire-adapted species in oak forests with mesophytic or shade-tolerant, fire-sensitive species may represent a change that is self-reinforcing, as microenvironmental conditions are altered in a way that continually improves them for mesophytic species (cooler, damper, more shaded conditions; less flammable litter layer) and deteriorates them for shade-intolerant, fire-adapted species.  These changes, along with the loss of fire-adapted species pools and the establishment of exotic invasives, reduce the ability of fire-adapted communities to recover even if fire disturbance returns.  This may make the reintroduction of fire challenging and maybe impossible on all but the more xeric, nutrient-poor sites, thus limiting restoration potential (Nowacki and Abrams 2008).

Significant impacts to Wisconsin’s forests are expected from projected changes in climate over the next 100 years.  Future conditions may include increases in average temperatures; changes in precipitation and soil moisture; longer growing seasons; shorter winters; and more severe storm, flood, and drought events.  However, effects will vary by forest type and location, and specific effects are difficult to predict.  The picture for oaks is mixed.  Some species of oaks and hickories may increase with warmer temperatures, but how oak-hickory forests would respond to long-term changes in moisture patterns is uncertain.  Invasive species, already seriously impacting oak forests, also are expected to increase and become more aggressive as a result of warmer temperatures and increased concentrations of carbon dioxide in the atmosphere.  Insect pests and pathogens may also increase (WICCI 2010).

Land ownership and use patterns in southern Wisconsin forested landscapes present significant challenges for oak management.  The majority of these forests are in private ownership so the decisions of private landowners, which are affected primarily by various socio-economic factors, have a direct bearing on the future of oak forests.  For example, the increase in rural housing development in forested landscapes due to their recreational and aesthetic amenities, and the resulting rise in land values, has made the division and sale of all or a portion of their land holdings very attractive to landowners.  Such parcelization, or division of ownerships into smaller and smaller parcels, contributes to forest fragmentation and makes implementing certain management practices, such as timber harvesting or prescribed fire, more difficult.  The recent high market price for sugar maple, the challenge and expense associated with regenerating oak in the presence of shade-tolerant competition, invasive plants, insects, and heavy deer herbivory, and the short-term decrease in aesthetic appeal that often follows oak regeneration practices can discourage landowners from adopting these practices, particularly if they intend to own their parcel only for a short time (Knoot et al. 2010).  Understanding the factors that influence landowner decisions, engaging and educating private landowners on the conservation significance of oak, and developing approaches that address the constraints to oak management will be critical to the persistence of oak in southern Wisconsin forests.

The definition of a “healthy” or “high-quality” oak forest depends on many factors and should be viewed in terms of a forest stand’s role within a larger oak ecosystem, for example, within a 10-100 sq. mi. area.  Such landscapes should include stands ranging from regenerating to mature and old-growth, and may incorporate those maintained by fire, timber harvest, other means (e.g., mechanical or chemical understory treatment, planting, deer exclosures), or combinations of these.  Essential to this scenario is the control of exotic invasives, and maintenance of deer population levels that allow oak to regenerate.  Dry-mesic to mesic sites with an overstory of mature oaks gradually succeeding to mesophytic species may be considered high-quality from either a commercial or ecosystem perspective, though oak regeneration may be unfeasible and the oak component will disappear.  On more xeric sites, regeneration may occur more readily with appropriate management that usually includes harvest, and perpetuate the cover type in the stand.  Former fields and cutovers planted to oaks can provide quality habitat and develop into oak forests or woodland.  For the full range of oak ecosystem plants and animals to thrive, fire will be necessary somewhere in the landscape.

As with other forest types, the quality of oak forests increases with tract size, which maximizes management options such as fire and timber harvest, and insulates stands from the effects of hard edges (e.g., high deer populations and invasive plants).

Related WBCI Habitats: Central Hardwood, Oak Barrens, Oak Opening, Scrub Oak, and, to the extent that oak is present, Northern Hardwood and Bottomland Hardwood.

Overall Importance of Habitat for Birds

Oaks dominate the forested landscapes of southern Wisconsin and provide critical habitat for a diversity of birds, including most breeding forest species of conservation concern in the south.  Common breeding species that are present across the moisture continuum from dry to mesic include Hairy Woodpecker, Downy Woodpecker, Red-bellied Woodpecker, Eastern Wood-Pewee, Blue Jay, Black-capped Chickadee, White-breasted Nuthatch, Blue-gray Gnatcatcher, Red-eyed Vireo, Ovenbird, Scarlet Tanager, and Rose-breasted Grosbeak.  Species of high conservation priority that rely heavily on this forest type include Whip-poor-will and several area-sensitive birds such as Wood Thrush, Cerulean Warbler, Worm-eating Warbler, and Hooded Warbler.

A host of different factors influences what bird species are found in a particular tract.  These include site-specific factors such as tree size, height, and age, canopy closure, tree species diversity, and understory structure (e.g., shrub and sapling density), which are affected by disturbance or management history as well as by soil conditions and local topography.  Bird communities also are determined in part by geographic location (especially near the edges of ranges) and by landscape characteristics such as forest tract size and configuration and surrounding habitats and land uses.  Populations of individual bird species respond differently to the complex interplay of these factors.  Although summarizing this for the entire bird community is problematic, some general trends are apparent, for example, in terms of two factors with implications essential to management: disturbance and landscape.

In an oak stand following a severe wind event or an even-aged regeneration timber harvest (overstory removal, clear-cut, coppice, seed tree, or 2nd-cut shelterwood) that leaves few or no trees left standing, the bird assemblage changes in a fairly predictable way as the stand passes through successional stages.  Recently cleared stands with open herbaceous cover and many shrubs and young saplings attract early-successional and shrub-nesting species such as House Wren, Gray Catbird, Common Yellowthroat, Song Sparrow, Eastern Towhee, and Priority species Ruffed Grouse, Black-billed Cuckoo, American Woodcock, Northern Flicker, Blue-winged Warbler, and sometimes Red-headed Woodpecker if many snags remain.  Stands in open or semi-open surroundings may also have Priority species such as Field Sparrow or Brown Thrasher.  As the forest succeeds to dense saplings, the community simplifies: these species disappear (to the extent that shrubby openings do not persist) and are replaced by a few forest species, mostly generalists, such as Downy Woodpecker, Blue Jay, Black-capped Chickadee, American Robin, American Redstart, and the Priority species Rose-breasted Grosbeak and, sometimes (to the extent that canopy trees remain), Wood Thrush.  As the forest develops into pole timber, these same species (except American Redstart and Wood Thrush) may remain, with the addition of Least Flycatcher, Red-eyed Vireo, and Ovenbird.  After many decades, the maturation of the oak forest typically adds common forest species such as Eastern Wood-Pewee and Scarlet Tanager and the Priority species Yellow-billed Cuckoo, Yellow-throated Vireo, and Wood Thrush.

When disturbance is partial, from scattered windthrown trees, minor tree disease or insect outbreaks, or timber harvests (e.g., thinnings or 1st-cut shelterwoods) that leave many mature trees within a matrix of low herbaceous and rank woody growth, many of the same early successional species occur.  However, several other Priority birds may also be found including Veery, Mourning Warbler, higher numbers of Blue-winged Warbler and Rose-breasted Grosbeak, and many forest canopy species.  If these disturbed stands are embedded within an extensively forested landscape, then several additional Priority “interior edge” species such as Chestnut-sided Warbler, Kentucky Warbler, and Hooded Warbler often occur.  These partially disturbed stands maintain a more diverse blend of early and late successional species throughout their development, compared with cleared stands.  In forested tracts larger than about 500 acres, or in smaller tracts within an extensively forested landscape, mature forest may also provide breeding habitat for forest interior specialists including Cerulean Warbler, Worm-eating Warbler, Broad-winged Hawk, and (in mesic microsites) Acadian Flycatcher (Mossman and Hoffman 1989, M.J. Mossman pers. comm. 2011).

The avifauna of fire-maintained oak woodland is not well documented because of the dearth of woodland stands, their relatively brief tenure under woodland management, and their typically small size, which increases the influence of surrounding habitats.  Surveys in managed Driftless Area woodlands suggest that the same range of bird species use these stands, as in unburned oak forest, when the vigor of canopy oaks is maintained.  The woodland’s more open understory may reduce numbers of species such as Veery, Rose-breasted Grosbeak, American Redstart, and Chestnut-sided Warbler, and ground-fires may temporarily reduce the abundance of Ovenbirds but increase numbers of American Robins and House Wrens.  When forests of oak and mixed mesophytic species are restored to oak woodland by fire and the removal of fire-sensitive trees, it may increase numbers of open-canopy species such as Baltimore Oriole, Great Crested Flycatcher and (if adjacent to more open habitats) Eastern Bluebird and some interior edge species such as Mourning Warbler, Gray Catbird and Blue-winged Warbler, which take advantage of dense shrub patches responding to canopy openings.  These patches of dense understory often come and go with the dynamics of woodland ground fires (M.J. Mossman pers. comm. 2011).

Within these relationships of tract age and landscape characteristics, the prevalence of oak species also is important, though perhaps less well understood.  Oak acorns are an important food source for many bird species, including Ruffed Grouse, Wild Turkey, Blue Jay and Wood Duck (WDNR 2011b), and insects associated with oaks have recently been shown to support high densities of migrant and breeding songbirds (Wood 2011).  Many birds, including Priority species (e.g., Red-headed Woodpecker, Cerulean Warbler, and especially Whip-poor-will and Worm-eating Warbler) appear to be associated with oaks or oak-dominated forests, and it is uncertain to what extent these relationships are due to a preference for some ecological attribute of the oak species, or to the forest structures associated with them (e.g., semi-open canopy and an understory that may range from open herbaceous to dense woody growth).

WBCI Priority Bird Species.  Species in boldface are currently proposed as Focal species for southern Wisconsin forests.

Species name Status Habitat and/or Special Habitat Features
Ruffed Grouse bwf Now uncommon to rare, gone from many former areas; where patches of both early-successional and older forest occur.
Red-shouldered Hawk bmwf In extensive tracts adjacent to floodplain forest; nest in large trees.
Broad-winged Hawk bm In extensive tracts.
American Woodcock bmf In early-successional tracts, large openings; may feed in forest.
Black-billed Cuckoo bM Shrubby woods and edge.
Yellow-billed Cuckoo BM Fairly common; prefers large tracts, canopy.
Whip-poor-will bm Disappearing; prefers dry oak forest or woodland with open understory, near openings; often in bedrock glades or oak barrens succeeded to forest.
Chimney Swift bmf? Nests in chimneys, occasionally in large “chimney” snags within oak forest.
Red-headed Woodpecker bmwf Where barkless snags occur due to windthrow, fire, or disease; also in open-canopy patches; more common in oak woodland.
Yellow-bellied Sapsucker bmw Especially near floodplain forest, in Driftless Area coulees, and where white birch or aspen are present.
Northern Flicker BMw Scattered, where snags, open or semi-open canopy, open herbaceous understory; prefers drier sites.
Acadian Flycatcher bm Occasional along streams, at bases of steep slopes or in well-shaded mesic microsites in interior of extensive forest.
Least Flycatcher BM Fairly common but irregular in both interior and edge, including pole-sized stands; often in colony-like breeding groups.
Yellow-throated Vireo BM Common and widespread in mature forest tracts >40 acres.
Veery BM Extensive dry-mesic forest where there are dense shrubs or rank, tall, diverse forest herb layer, especially damp or mesic microsites.
Wood Thrush BM In tracts >40 acres, where closed or semi-open canopy, especially with patches of tall semi-dense saplings.
Brown Thrasher bm Open oak woodland adjacent to more open habitats; edges.
Blue-winged Warbler BM Dry-mesic to mesic, shrubby forest openings, edges.
Golden-winged Warbler bm Rare; in same sites as Blue-winged Warbler.
Chestnut-sided Warbler bM Rare breeder in shrubby openings and edges of extensive forest; more common northward.
Black-throated Green Warbler bM Rare breeder, in large, mature, dry-mesic to mesic tracts that include sugar maple or sometimes conifers (white pine, hemlock).
Cerulean Warbler BM Mature forest with tall (>75 ft. high), diverse canopy species and structure; extensive tracts.
Worm-eating Warbler bm Mature oak forest with semi-open canopy on south and west-facing slopes, draws; large tracts.
Louisiana Waterthrush bm Along clear, rocky streams or springs within extensive forest.
Kentucky Warbler bm Uncommon in dry-mesic to mesic forest tracts >240 acres; often in dense or semi-dense damp, shrubby openings of natural or logging origin, and floodplain-upland boundary.
Mourning Warbler bm Similar to Kentucky Warbler, but more common, less restricted to very large tracts, extends into larger open-canopy patches.
Hooded Warbler BM Interior openings with dense shrubs and brambles; large tracts; prefers mesic or dry-mesic sites; uses pine plantations with shrubby understories in the Kettle Moraine.
Rose-breasted Grosbeak BM Common and widespread in forest interior or edge; prefers open or semi-open canopy with moderate sapling/shrub growth.


The Upper Mississippi River and Great Lakes Joint Venture Implementation Plan (UMRGLJV 2007) assigns Wisconsin a habitat objective for Deciduous Forest of 4,199 acres for Management and Protection and 4,199 acres for Restoration and Enhancement, using Cerulean Warbler, Louisiana Waterthrush, and Kentucky Warbler as focal planning species.  These objectives are based on BCR 23 and Wisconsin population estimates and goals for these species that are extremely low because they are extrapolated from data of the federal BBS, a survey that does not adequately sample these rare species or their habitats well.  Lacking reliable estimates for these species makes it difficult to set a numeric habitat objective for oak forests using a focal-species approach.  Additional complications arise from the fact that several focal species seem to require particular stand or site-level structural attributes in addition to forest cover, attributes which are challenging to quantify, map, and track over time.  The WBCI Southern Forests committee recommends generating better population estimates and long-term monitoring for all oak forest focal species.  In the interim, the committee suggests a goal to maintain focal species populations within oak forests in the Wisconsin portion of BCR 23, at least for those species monitored in local landscapes (e.g., Baraboo Hills, Lower Wisconsin River, Fort McCoy) or region-wide (e.g., Whip-poor-will, American Woodcock).

Management Recommendations

Oak is an important resource for birds and other wildlife.  While oak currently is relatively abundant in southern Wisconsin forests, it is not being replaced.  Given current management practices, past land use history, forest condition (abundance of mesophytic competitors), and ecological stressors (invasives, herbivory) it is unlikely that oak will be maintained into the future at its current level of importance.  In many situations successful regeneration will require attention to site selection, canopy disturbance, repeated control of competing vegetation, reduced herbivory, and the use of fire.  Oak regeneration is best characterized as a process rather than a single event, one that necessitates the commitment of management effort and resources at various critical points during the life of a stand.  Effective tools and techniques do exist, and others may be developed.  Successfully regenerating oak presents challenges, yet failure to make the attempt and the concomitant decline of oak across the landscape may represent an unacceptable loss for birds and other wildlife.  Forest managers and conservationists will need to develop a long-term, adaptive approach that both allows for successional regeneration and produces measureable gains for priority southern forest birds.

Landscape-level Recommendations

  1. Plan oak forest and woodland management on a landscape scale to provide the full range of structures, age and size classes, and successional stages, and to determine the most appropriate sites for restoration.  The tiered landscape scheme described in Wilson (2008) for the Driftless Area may provide a useful initial decision-making tool for focusing interior-forest bird management (Tier 3 landscapes), forest connectivity and oak regeneration (Tier 2 landscapes), and management for other less forested or non-forested communities (e.g., savanna, prairie; Tier 1 landscapes).
  2. Protect and connect existing tracts of oak forest, especially older forest which currently is lacking and which provides important habitat for various priority birds (WDNR 2008 a, b, c; 2005).  Modeling has shown that % forest is an important landscape-level habitat suitability feature for many priority forest birds (Thogmartin and Knutson 2007; Thogmartin et al. 2004).
  3. Retain some patches across the landscape where managed old-growth is the goal or where harvest is excluded and the forest is allowed to mature naturally (Bakermans and Rodewald 2009).
  4. Manage oak forests and woodlands as part of a natural gradient from forest to woodland to savanna (WDNR 2008 a, b, c).
  5. Where feasible, encourage use of prescribed fire to regenerate, restore, and maintain oak forests and woodlands (WDNR 2008 a, b, c; Staffen 2010; see multiple references in Site-level Recommendations, below).
  6. Restore oak forests and woodlands on appropriate sites.  Utilize landscape context (e.g., size of tract, nature of surrounding habitat, regional abundance and location of  similar forest types, etc.) and site-specific factors (e.g., soil, topography, presence of savanna indicator species in the groundlayer, etc.) to determine whether forest or woodland may be most appropriate (Staffen 2010).  From a bird habitat perspective, smaller or isolated tracts may be more suited for savanna management (Brawn 2006).
  7. Although deer herbivory is a local and seasonal phenomenon, it is directly affected by landscape-scale population numbers.  Based on observed deer density effects in Wisconsin, deer populations should be maintained at about 50% of natural carrying capacity in order not to impede oak regeneration (WDNR 2011b).
  8. Maintain a diversity of oak species across the landscape (WDNR 2008 a, b, c, 2011b).  Recent research suggests that white oak may be particularly important to priority species such as Cerulean Warbler for both nesting and foraging (Bakermans and Rodewald 2009; Newell and Rodewald 2011; M.J. Mossman pers. comm. 2011).
  9. Develop landowner incentives to preserve, restore, and manage oak forests and woodlands (WDNR 2008 a, b, c).
  10. Educate private landowners on the conservation importance of oak (Knoot et al. 2010).
  11. Encourage cross-boundary cooperation among landowners in order to more effectively and efficiently manage oak (Knoot et al. 2010).

Site-level Recommendations

  1. Articulate clear site-level management objectives that have been developed within a landscape context.  Options for managing oak ecosystems (i.e., where harvest in order to realize income is not the primary consideration) vary from those for timber production, although there is overlap.  Modifying silvicultural systems designed to maximize timber products in order to integrate other objectives, such as wildlife habitat, may result in some reduced commercial timber value (WDNR 2011b).  However, integrating ecological objectives, such as native plant diversity and structural features that provide wildlife habitat, is likely to result in better outcomes for priority birds (WDNR 2011c).
  2. Site selection is critical to oak regeneration success.  In general, more intensive management will be needed on mesic sites for oak to be at least a partial component of the future stand.  Control of competing vegetation is essential.  Timber cutting for oak regeneration should not be attempted, particularly on mesic or dry-mesic sites, if land managers or landowners are unable or unwilling to conduct the necessary pre- and post-harvest treatments, as this will almost certainly result in conversion to mesophytic species.
  3. Wherever feasible, strongly consider combining fire with silvicultural prescriptions (shelterwood; group selection; thinning) to regenerate oak.  These techniques have shown substantial benefits for oak regeneration in other parts of the country (east, southeast, elsewhere in the Midwest), and also Wisconsin (Kruger and Reich 1997) including on productive sites (Kruger and Reich 1997; Brose et al. 2006; Dey and Fan 2009; Dey et al. 2010), with positive effects persisting for at least a decade (Brose 2010).
    • Medium-to-high intensity prescribed fire conducted in spring during leaf expansion has shown the most promise as a regeneration technique in combination with a shelterwood harvest (Brose and Van Lear 1998; Van Lear et al. 2000; Dey and Fan 2009; Brose 2010).  This technique may also be attractive to private landowners as the harvesting produces income that covers the costs of the prescribed burn.
    • Fire can be used to reduce litter layer and favor seedling establishment before harvest and to control competition and enhance oak competitive status after a harvest or thinning (Franklin et al. 2003; Albrecht and McCarthy 2006; Brose et al. 2006; Dey and Fan 2009).
    • Coordinate burns with silvicultural practices and acorn production.  Allow several fire-free years after a large mast year, harvest, or thinning so oak seedlings can develop enough below-ground reserves to resprout after fire and the seeds of fire-sensitive oak competitors can germinate so fire can kill them (Brose and Van Lear 1998; Brose et al. 1999; Hutchinson et al. 2005; Brose et al. 2006; Dey and Fan 2009; Brose 2010).
  4. A shelterwood treatment that removes tall understory vegetation may be effective in regenerating oak, especially in dry-mesic sites.  Underplanting with oak seedlings can increase the chance that oak will be a significant component of future stand, especially in mesic situations (Povak et al. 2008).
  5. Management activities must be monitored to ensure that oak regeneration succeeds and that follow-up treatments are conducted when necessary (WDNR 2008 a, b, c, 2011b).  Only long-term monitoring will prove the efficacy of regeneration techniques (Brose et al. 2006; Povak et al. 2008; Brose 2010).
  6. Excessive deer herbivory may be the limiting factor for oak regeneration in many areas, and must be addressed in order for regeneration to succeed.  Protecting regeneration from browsing is expensive and labor intensive.  No regeneration technique is likely to work if deer browse is too high (Brose et al. 2006; Povak et al. 2008; WDNR 2011b).
  7. Control invasive species, especially garlic mustard, buckthorn, and honeysuckle, and eliminate where possible; employ management practices that limit the spread of invasives (WDNR 2008 a, b, c).  Refer to WDNR Forestry Best Management Practices (BMPs) for invasive species (WDNR 2009).  Care should be taken when deciding where to treat stands of oak with Btk, a bacterial insecticide used to control gypsy moth, as this substance can affect food sources for insectivorous birds.
  8. Limit or exclude livestock grazing.  Heavy grazing can alter understory plant composition, damage trees, hinder regeneration, and cause soil compaction.  Cattle also lead to increased nest parasitism by attracting Brown-headed Cowbirds (Knutson et al. 2001).
  9. In general, managing for oak should be compatible with priority forest bird habitat if planned and conducted within an appropriate landscape context.
    • Oak regeneration practices (including those that combine silviculture with prescribed fire) should have no long-term negative impacts on priority forest-interior birds if the surrounding landscape is forested.  Interior forest species that are attracted to canopy gaps or patches of herbaceous or woody vegetation (e.g., Cerulean Warbler, Kentucky Warbler, Wood Thrush) may benefit from practices such as shelterwood, selection cuts, and thinnings that create canopy openings in mature forest (Stoleson 2004; Lanham et al. 2006; Bakermans and Rodewald 2009; Dey et al. 2010).
    • Retain some large canopy oaks to provide nesting and foraging habitat for canopy birds and as acorn sources (Lanham et al. 2006; Newell and Rodewald 2011).
    • Retention and recruitment of cavity trees, snags, and coarse woody debris within a harvested area provide structural features needed by birds associated with mature forests.
    • Some stands should be managed with extended rotations to provide habitat for birds that require forest with old-growth characteristics (Bakermans and Rodewald 2009).
    • Interior forest species can use oak woodland or more closed-canopy savanna if it is adjacent to or embedded in closed-canopy forest (M.J. Mossman pers. comm. 2011).
  10. Management for Cerulean Warbler habitat should benefit other priority forest-interior birds, as this species requires extensive tracts of mature or old-growth forest (Knutson et al. 2001).  Hamel and others (Hamel 2006; Hamel and Rosenberg 2007) have attempted to articulate forest management prescriptions for this species in various parts of its range, including other portions of the Midwest (though not Wisconsin).  Knutson et al. (2001) propose a Cerulean Warbler Conservation Area Model for BCR 23, which includes Wisconsin.  Though these recommendations have not been tested in Wisconsin, they are based on detailed descriptions of the species’ range-wide habitat associations and largely concur with what is known of Cerulean Warbler habitat use in Wisconsin.  As the species seems to heavily favor oak in Wisconsin, the following recommendations are worth including here:
    • While Cerulean Warblers in the Midwest use tracts ranging widely in size, stable or source populations require thousands of acres of mature forest.  Knutson et al. (2001) recommend a mature forest core of ≥1,730 acres with low edge-to-area ratio within a ≥10,000 acre forested matrix.  Prescriptions to favor or accommodate habitat for this species should be attempted preferentially in landscapes and sites that meet these characteristics.
    • Studies of Cerulean Warbler habitat across its range have repeatedly documented mature, tall, well-spaced canopy trees with spreading crowns, heterogeneous vertical distribution of vegetation, and small canopy gaps in occupied sites.  This suggests stands with tall sawtimber trees, moderate stand stocking (65-85%), and a relatively high quadratic mean diameter (Hamel 2006; Hamel and Rosenberg 2007).
    • Silviculturally, variable retention shelterwood may be an appropriate management technique for oak in sites occupied or with the potential to be occupied by Cerulean Warblers.  Experimental prescriptions for Cerulean Warblers in Ohio, Tennessee, West Virginia, and Arkansas are described in Hamel (2006), Hamel et al. (2006), and Hamel et al. (2010).

Ecological Opportunities

Ecological Landscape Opportunity Management Recommendations
Central Sand Hills Major All
Central Sand Plains Major All
Southeast Glacial Plains Major All
Southwest Savanna Major All
Western Coulee and Ridges Major All
Central Lake Michigan Coastal Important All
Southern Lake Michigan Coastal Important All
Western Prairie Important All
Forest Transition Present All

Research Needs

  1. Regeneration trials combining silviculture with prescribed fire and that include a long-term (at least 10-20 years) monitoring component are needed in southern Wisconsin, particularly on dry-mesic and mesic sites, to test oak regeneration techniques that have proved successful elsewhere in the country (Kruger and Reich 1997; Brose et al. 2006; Dey and Fan 2009; Brose 2010; Dey et al. 2010).
  2. More research is needed to assess private landowner perspectives on oak management and on methods to successfully engage them in this endeavor (Knoot et al. 2010).
  3. Investigate the short- and long-term effects of different silvicultural treatments on breeding birds in oak forests (e.g., by conducting pre- and post-harvest bird surveys and habitat characterizations).
  4. Assess the landscape and stand-level recommendations for managing habitat for Cerulean Warblers provided by Knutson et al. (2001), Hamel (2006), and Hamel and Rosenberg (2007) for applicability to southern Wisconsin.  Develop and test similar recommendations for southern Wisconsin oak forests.
  5. Continue research to characterize Cerulean Warbler distribution and habitat selection on the Lower Wisconsin River; seek funding to expand research to other extensive forest landscapes in southern Wisconsin.


Key Sites

Key Partners

Funding Sources

Information Sources


Contact Information

Steele, Y.  2012.  Oak Habitat Page.  In Paulios, A. and K. Kreitinger (eds.).  2007-2012.  The Wisconsin All-Bird Conservation Plan, Version 1.0.  Wisconsin Bird Conservation Initiative.  Wisconsin Department of Natural Resources, Madison, WI.

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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