Idle Cool-season Grasses and Forbs

Photo by Greg Kidd, NRCS.

Habitat Description

Habitat Crosswalk

Sample and Mossman: Idle Cool-season Grasses and Forbs (Sample and Mossman 1997).
Vegetation of Wisconsin: N/A (Curtis 1971).
Wisconsin Department of Natural Resources Natural Communities: Surrogate Grasslands (WDNR 2005).


Despite some similarity to prairies, idled grasslands such as Idle Cool-season Grasses and Forbs are considered surrogate grasslands rather than a native prairie community. They often occur on agricultural lands that are taken out of production and idled for extended periods of time. Examples include retired hayfields and pastures, grasslands planted for wildlife habitat on public lands, and agricultural fields that are retired through the Conservation Reserve Program (CRP) or other set-aside programs (Sample and Mossman 1997, McCoy et al. 2001b, WDNR 2005). These programs encourage landowners to convert highly erodible cropland to long-term vegetative cover, such as warm- or cool-season grasses. Cool-season mixes grow best during the spring and fall and are composed primarily of non-native grasses and forbs. Shortgrass mixes (0-15cm in height) can include Kentucky bluegrass, Canada bluegrass, June grass, redtop, and poverty oat grass; medium-height mixes (15-35cm) can include smooth brome, timothy, orchard grass, and quackgrass; tallgrass mixes (35-60cm) can include reed canary grass, bluejoint grass, and tall fescue. Some stands also have a substantial legume component and may include alfalfa and red clover. Recently planted fields can have an abundance of annual weeds and bare ground but typically mature to a moderately dense cover of grass with a substantial little layer if left undisturbed (McCoy et al. 2001a). Idled grasslands are always undisturbed during the nesting season but can remain unmanaged for many years.

Historical and Present-day Context and Distribution

During the nineteenth century, diverse prairie communities were largely eliminated in favor of small grains, grass hay, and permanent pastures. Although these changes destroyed or significantly altered most native grasslands, the landscape remained largely rural with small farmsteads interspersed with idled or undeveloped lands. Many birds and other wildlife adapted to these changes and used the diverse farmlands as surrogate grassland habitats (Warner 1994). By the mid-twentieth century, however, urban development increased and large farming operations began to displace the more rural land-use patterns (Sample and Mossman 1997, Sample et al. 2003, WDNR 2005). Many pastures were replaced by intensively-managed row crops, hayfields were harvested earlier and more frequently, and housing developments fragmented the landscape and created movement corridors for predators.

Changing land use has led to a decline in the quality and quantity of grassland habitat and, most likely, fewer idled grasslands. Idled grasslands are difficult to inventory, however, because of their ephemeral nature. Lands idled one year can be back in production the following year and even lands enrolled in conservation programs are not necessarily idled (i.e., managed haying and grazing is often allowed) or protected in perpetuity. CRP contracts typically last 10-15 years with no guarantee of re-enrollment after they expire. Although there are currently 15,368 hectares of CRP fields planted to cool-season grasses in Wisconsin, this figure has declined in recent years (FSA 2006, 2008). Renewed interest in corn ethanol and other market factors have led to high corn prices, creating additional pressure on remaining CRP acres (Murray and Best 2003, Roth et al. 2005, Bies 2006). However, some perennial grasses (e.g., switchgrass) produce more energy per unit of input than corn and may provide a more ecologically-sustainable energy source (Bies 2006). Also, the harvest of grass biomass crops could result in a mixture of harvested and non-harvested fields and thus add idled grassland habitat to the landscape (Murray and Best 2003, Roth et al. 2005, Herkert 2007).

Natural Disturbances and Threats

Idle Cool-season Grasses and Forbs habitats lack the disturbances inherent to other grassland habitats. Unlike native prairie remnants in Wisconsin, idled grasslands typically are not disturbed by prescribed fire, mowing, or herbicide spray nor are they actively grazed, hayed, or farmed. Lacking any form of disturbance, they can experience substantial changes in their structure and composition over time (Greenfield et al. 2003). For instance, idled grasslands fragmented by woodlots or other human developments are threatened by encroaching woody vegetation (Steinauer and Collins 1996, Briggs 2005). Invasive woody species such as buckthorn, hawthorn, dogwood, box elder, multiflora rose, and sumac can shade out the early-successional grassland plants and cause rapid structural changes that are unacceptable for most grassland birds (Hoffman and Sample 1988, Sample and Mossman 1997). Changes in agricultural practices also pose a significant threat to idled grassland habitats. Intensively-managed row crops with little wildlife value have replaced the idled pastures and hayfields used by many grassland bird species. Also, the recent shift from late-grass to alfalfa hay has reduced the amount of time between harvests and further reduced the amount of idled grasslands on the landscape (Sample and Mossman 1997).

Related WBCI Habitats: Dry-mesic Prairie, Wet-mesic Prairie, Idle Warm-season Grasses and Forbs, Fallow Field.

Overall Importance of Habitat for Birds

Several factors influence bird use of Idle Cool-season Grasses and Forbs habitats. The length of time a field has been idled will affect its suitability for certain species. Recently planted fields often contain bare ground and sparse vegetative cover and thus provide habitat for Upland Sandpiper, Horned Lark, Vesper Sparrow, Grasshopper Sparrow, Western Meadowlark, and other shortgrass species. As the fields age, litter accumulates, height-density of the herbaceous vegetation increases, and conditions become more suitable for mid to tallgrass species. Generalist species such as Sedge Wren, Common Yellowthroat, and Red-winged Blackbird are the dominant breeders in tallgrass warm-season mixes and less common nesting species include Henslow’s Sparrow, Bobolink, Eastern Meadowlark, and Dickcissel (Sample and Mossman 1997, Best et al. 1997). Although Northern Harrier is not a common breeder in any grassland habitat, it preferentially nests in undisturbed grasslands with tall, dense cover such as Idle Cool-season Grasses and Forbs (Herkert et al. 1999). Idled grasslands with scattered shrubs also can support structure-nesting species such as Loggerhead Shrike, Bell’s Vireo, Clay-colored Sparrow, and Field Sparrow.

Landscape context also influences how birds may use idled grassland habitats. Fields of Idle Cool-season Grasses and Forbs adjacent to hayfields or other disturbed lands provide secure areas for second nest attempts after mowing-induced failure (Sample and Mossman 1997). Also, small idled fields located in close proximity to other extensive grassland areas increase the overall size and heterogeneity of the surrounding landscape and thus improve conditions for species requiring large grassland patches. Area-sensitive species such as Northern Harrier, Short-eared Owl, and Greater Prairie-Chicken readily nest, forage, and roost in small patches of idled grassland that are embedded within a high-grassland landscape (Sample and Mossman 1997, Herkert et al. 1999). Other species such as Northern Bobwhite and Ring-necked Pheasant rely on the residual cover of idled grasslands during winter months, emphasizing the importance of these habitats at all times of the annual cycle (Walk 1998, Brennan 1999).

Priority Birds

Species Status Habitat and/or Special Habitat Features
Mallard b If appropriate open water for breeding pairs and broods is available nearby.
Blue-winged Teal b If appropriate open water for breeding pairs and broods is available nearby.
Sharp-tailed Grouse b, w Occurs in idled grassland habitats within high-grass landscapes.
Greater Prairie-Chicken b, w Occurs in idled grassland habitats within high-grass landscapes.
Northern Bobwhite b, w Requires brushy areas adjacent to idled grasslands.
Northern Harrier b, m May occur in idled grasslands embedded within a large, grassland-dominated area.
Upland Sandpiper b, m Occurs in high-grass landscapes with some drier ridges and hummocks.
Barn Owl f Very rare resident in southern and central Wisconsin.
Short-eared Owl b, m, w May occur in idled grasslands embedded within a large, grassland-dominated area.
Willow Flycatcher b, m Requires a shrub component.
Sedge Wren B, M Prefers dense herbaceous cover dominated by grasses or sedges and thick litter layer.
Loggerhead Shrike b, m Very rare breeder in Wisconsin. Requires a shrub component.
Bell’s Vireo b, m Requires a shrub component.
Brown Thrasher b, m Requires a shrub component.
Common Yellowthroat B, M Prefers tall, dense herbaceous cover and/or a shrub component.
Clay-colored Sparrow b, m Requires a shrub component.
Field Sparrow b, m Requires a shrub component.
Vesper Sparrow b, m Prefers areas with short, sparse vegetation and some bare ground.
Grasshopper Sparrow b, m Prefers relatively short, patchy vegetation.
Henslow’s Sparrow b, m Prefers tall, dense herbaceous cover that is grass-dominated with a substantial component of residual vegetation.
LeConte’s Sparrow b, m  
Dickcissel b, m Prefers sites with a thick-stemmed forb component and medium-height grass.
Bobolink B, M  
Eastern Meadowlark B, M  
Western Meadowlark b, m Prefers relatively short vegetation and <5% woody cover.


  1. Buffer idled grasslands with other grassland habitats.
  2. Protect, maintain, and restore 383,000 hectares of grassland habitat in Wisconsin to sustain regional breeding populations of grassland birds (Potter et al. 2007).
  3. Increase public awareness of the conservation values of surrogate grassland habitats.

Management Recommendations

Landscape-level Recommendations

  1. Support state and federal programs that manage, enhance, or restore grassland habitats on private lands. Develop cooperative agreements with private landowners to prevent habitat fragmentation and conversion in areas critical for grassland bird conservation.
  2. Determine what scale of landscape management is possible in an area: medium (400-2,000 hectares) or large (>4,000 hectares). Consider developing a grassland Bird Conservation Area in appropriate landscapes (see Fitzgerald and Pashley 2000).
  3. Increase inter- and intra-agency coordination to maximize benefits of grassland conservation projects.
  4. Develop a digital layer of high-grassland landscapes to focus restoration and conservation efforts. Discourage extensive tree planting within these landscapes to improve the long-term viability of obligate grassland birds.
  5. Partner with the agricultural community to ensure rural working landscapes with high amounts of open space suitable for birds and other wildlife.
  6. Encourage longer contracts for short-term set-aside programs (>3 years). Enforce guidelines that cover is planted and managed appropriately (Warner et al. 2000). 

Site-level Recommendations

  1. Include grasses of varying heights in seed mixes to promote a variety of height and density among fields, including short cool-season grasses such as Kentucky bluegrass and redtop (Sample and Mossman 1997).
  2. Reduce grass seeding rates by up to 50% (4-6 lb per acre for cool-season grasses) to reduce vegetation density and to encourage forbs (Sample and Mossman 1997).
  3. Include enough forb seeds in mixes to result in at least 10% forb cover. In most cases, 10,000-20,000 forb seeds per acre should produce a noticeable forb component (Sample and Mossman 1997).
  4. Enroll whole fields into conservation programs to avoid linear-shaped fields with high edge:interior rations (Sample and Mossman 1997).
  5. Remove linear woody features such as hedgerows and woody fencelines as well as woodlots to improve site suitability for obligate grassland birds. Low density, scattered shrubs are acceptable and even required by some grassland birds such as Willow Flycatcher, Bell’s Vireo, and Brown Thrasher (Sample et al. 2003, WDNR 2005, Kost et al. 2007).
  6. Develop property-specific plans to control invasive species on idled grasslands, such as common and glossy buckthorn and box elder.

Ecological Opportunities

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

Research Needs


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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