Managing Habitat for Grassland Birds
A Guide for Wisconsin

Land Management Practices

Many management practices can be beneficial to grassland bird habitats. Because of the importance of idle grassland habitat it is generally important to rotate management through a given tract or area so that no more than approximately one-third of the land area is disturbed by any management technique or techniques in a given year (Herkert et al. 1996). Rotation of disturbances—such as mowing, grazing, harvesting, and burning—through subunits within a habitat block helps assure that some residual vegetation is always available for those species that require it. Rotation, especially in native grassland remnants, also provides refugia for potentially fire-vulnerable invertebrates and other fauna. It appears that a management subunit (i.e., the portion of a grassland block disturbed by management) may need to be at least 75 acres in size to maximize benefits for grassland birds (Herkert et al. 1996). In Wisconsin, most blocks of grassland habitat are not currently large enough to allow for subunits this size.

Mowing
Mowing is useful for controlling woody vegetation and weeds and can reduce the litter layer if cuttings are removed. Mowing can also alter plant species composition. For example, mid-summer mowing or burning of native warm-season grasses tends to suppress them and help develop and maintain native forbs, especially spring-flowering species, as well as cool-season grasses. Other native forbs are reduced by mid-summer mowing and benefit most from mowing or burning in the dormant season of early spring or late fall.

On private lands used for production agriculture, there are few recommendations that are currently both feasible to the farmer and beneficial to grassland birds. For example, delaying mowing until after 15 July is not likely to be considered by many dairy farmers—even with compensation—unless they are willing to let some fields go for use as feed for dry cows or other animals that do not require high-quality forage or if they want to let legumes re-seed themselves. One suggestion that has some merit is to cut hayfields from the inside out to allow escape routes for fledglings (Figure 7). In addition, locating idle nesting cover—such as old fields or set-aside lands—adjacent to hayfields provides alternate habitat for species that renest after mowing-induced failure of first nest attempts (Warner and Etter 1989).

Figure 7.  Diagram of mowing a hayfield from the inside out. Lines and arrows indicate the path of the tractor; "S" indicates the starting point.

On public and private lands managed for wildlife conservation purposes, it is advisable to delay mowing until after 15 July. Mowing after this date will allow most species a chance to raise at least one brood. However, in cases where late-nesting species such as dickcissels and sedge wrens are being managed for, mowing should be delayed until early August. If more than one mowing is conducted or if mowing is required after the breeding season for some other purpose, the last mowing of the year should generally be early enough to promote some fall regrowth, which provides residual vegetation cover the following spring. This means mowing should be done by early September (for cool-season grasses) or early August (for warm-season grasses) in most years.

Grassland birds respond to mowing in various ways:

• Some species abandon fields mowed during breeding activities, including bobolink, red-winged blackbird, dickcissel, sedge wren, ring-necked pheasant, eastern meadowlark, and Henslow's and swamp sparrow.

• Some species remain in cut fields to renest or increase in density after mowing, including upland sandpiper, savannah, grasshopper, and vesper sparrow, western meadowlark, and horned lark.

• Some species colonize recently cut fields or fields prior to spring green-up, primarily to forage. These include mourning dove, killdeer, common grackle, American robin, red-winged blackbird, northern flicker, rock dove, European starling, upland sandpiper, eastern meadowlark, and house sparrow.

• Many species do well in habitats that are mowed in the late summer or fall (annually or every few years). Exceptions include those species that require substantial residual vegetation early in the spring: Henslow's sparrow, sedge wren, ring-necked pheasant, and mallard.

Burning
Burning is typically used to control woody vegetation over time, reduce litter build-up, and stimulate grass and forb production. The timing of a burn can also influence plant species composition: spring burns tend to suppress cool-season grasses and promote warm-season grasses, while the opposite is true of mid- to late-summer burns. Again, the effects of burning depend on the bird species or groups targeted and on the intensity and completeness of the burn. Burns scheduled outside the breeding season—in spring from March to late April and in fall from September to November—are generally best for birds. As with mowing, burning cool-season grasses before mid-September or warm-season grasses by early August allows for some regrowth before dormancy. Fall burns generally are less complete than spring burns, leaving more stubble on the ground. As with other disturbances, no more than one-third of large areas (more than 100 acres) or one-half of smaller areas should be burned in a given year. Or, if small areas are in close proximity (i.e., less than one mile apart), some fields can be burned in their entirety, while leaving other sites unburned (Herkert et al. 1993). This alternative is not recommended for native grassland remnants where potentially fire-sensitive invertebrates may be a concern.

Prescribed burning is a useful management tool for grasslands. Grassland bird species have variable responses to burning, but over the long term many species benefit from 3-5 year burning rotations. Shown here is a burn at Spring Green Reserve in Sauk County.

Early spring (March and April) burning affects grassland bird species in different ways. In the breeding season immediately following the burn, some species do very well in burned areas, while others do not:

• Species with a positive response (i.e., species colonize field or increase in density) include killdeer; upland sandpiper; horned lark; vesper, lark, and grasshopper sparrow; eastern meadowlark; and Brewer's blackbird.

• Species with a negative response (i.e., species abandon field, fail to colonize fields, or are reduced in density) include mallard; northern pintail; northern harrier; ring-necked pheasant; mourning dove; sedge wren; common yellowthroat; clay-colored, Henslow's, Le Conte's, song, and swamp sparrow; and red-winged blackbird.

• Species reported to respond both negatively and positively include field and savannah sparrow, bobolink, and American goldfinch.

Over time, short spring burning rotations (every 1-2 years) reduce or remove woody vegetation and therefore lower the quality of habitat for species requiring shrubs or small trees. As shown above, one-year rotations also discourage species that require residual vegetation in the spring. Rotations of at least five years and longer tend to favor and maintain a woody component, such as upland shrub communities, and residual vegetation. Bird species that do not have significant requirements for litter or standing residual vegetation in spring will likely do well under short rotations, and most species appear adapted to moderate-length (3-5 year) burning rotations (Herkert et al. 1996).

Grazing
Grazing is used to control some species of woody vegetation, reduce litter build-up, and reduce vegetation height and density. Prickly and thorny shrub species, however, are actually encouraged by grazing (R. Henderson, DNR terrestrial ecologist, personal communication). Grazing results in a more diverse vegetation structure than either mowing or burning because of the uneven grazing patterns of cattle, which is related to factors such as the distribution of preferred and unpalatable plants and dung piles within pastures. Although grazing intensity can be varied, heavy grazing should be avoided. Light to moderate grazing is best. As a general guideline, leave more than 50% of grazed fields with a height of at least 10 inches (25 cm) or height-density measurements of at least 2-8 inches (5-20 cm). Defining grazing intensity and its effect on vegetation height and density in terms of stocking rate (animals per acre) is difficult, because of differences among years in precipitation and temperature and among sites in soil conditions and plant species composition (Skinner et al. 1984). All of these factors affect vegetation growth and therefore the amount of available forage, which in turn determines the appropriate stocking rate. In general, however, grazing at a rate of around 0.4-0.5 head of cattle per acre can be considered light grazing under average precipitation and soil conditions (George et al. 1979; D. Undersander, UWEX-Agronomy, personal communication; Sample 1995).

Large pastures that are lightly or moderately grazed, such as this one in Monroe County, provide good habitat for a number of species of management concern.

Native warm-season grass pastures can provide good habitat for a variety of grassland bird species (Skinner et al. 1984) and have the advantage of being left ungrazed until relatively late in the nesting season, when the forage quality of cool-season grass pastures has declined. However, warm-season pastures may require special management to maintain the warm-season grasses over time, such as by limiting the period of intense grazing in summer and by burning in late April or early May (R. Henderson, personal communication).

Large moderately grazed pasture in Marinette County.

Fall grazing should be stopped by early- to mid-September for cool-season grasses or early August for warm-season grasses, to allow for vegetation regrowth before dormancy sets in. The presence of several scattered shrubs or small trees, especially thorn-bearing species, increases the value of pastures as potential loggerhead shrike habitat.

As a general rule, bird species that prefer short vegetation occur in heavily grazed pastures, just as species preferring moderate and tall vegetation inhabit moderately and lightly grazed pastures, respectively. However, because pastures are often not grazed evenly, there is a likelihood that several ranges of vegetation height-density will be represented in a single pasture, especially large ones. The following are generalizations about species' responses to grazing from research in Wisconsin and the midwest:

• Tallgrass bird species such as sedge wren and Henslow's and Le Conte's sparrow are relatively intolerant of all but very light grazing.

• Light grazing can benefit species such as northern harrier, dickcissel, bobolink, and eastern meadowlark.

• Species that may occur in pastures that are moderately grazed include upland sandpiper, savannah and grasshopper sparrow, western meadowlark, and Brewer's blackbird.

• Heavily grazed pastures do not typically provide nesting habitat for any species of management concern, but are occasionally used for foraging. Nesting birds include horned lark and killdeer.

• Pastures with scattered shrubs can benefit loggerhead shrike, field and clay-colored sparrows, and Brewer's blackbird. Bell's vireo benefits from the presence of several dense patches of shrubs.

Planting and Restoration
Many grasslands managed for wildlife habitat have aimed for a tall and dense nesting cover. This cover was thought to be good for game birds such as ducks and pheasants. Recent research in Wisconsin, however, has shown that traditional monotypic stands of dense nesting cover may not be best for game birds (Gatti n.d.). Of the nongame grassland birds, only those species that prefer relatively tall, dense cover are attracted to such stands. More species would benefit from the establishment of shorter grasses, whether native or non-native (see section on long-term set-asides, below). Many wildlife managers are now experimenting with different seedings, especially with a variety of prairie plant species. Some of these restorations have provided excellent grassland bird habitat (Volkert 1992).

It is difficult to describe a seed mixture or seeding rate that guarantees a certain type of vegetation structure, because of variability in soil type and moisture, establishment techniques, and annual variation in precipitation. However, a general approach to lower vegetation height and density and to increase structural diversity is to lower seeding rates:

• Reduce cool-season grass seed to about 4-6 lb per acre, about half the normal rate.
• Make the following reductions for native warm-season grass mixes:
  • Switchgrass, use 2 lb per acre rather than the typical 4 lb;
  • Big and little bluestem, use 1 lb per acre rather than 2 lb;
  • Indiangrass, use 2 lb per acre rather than 3 lb
  • Side-oats grama, use 3 lb per acre (well-drained sites only).

It is also important to establish forbs in managed grasslands because they diversify structure and invertebrate resources. Several bird species such as dickcissel and savannah sparrow are most abundant in fields with a strong forb component. Reducing grass seeding rates, along with mowing or burning occasionally in the summer or fall, also helps encourage the forb component of a planting. Moreover, enough forb seed should be added to most mixes to result in at least 10% forb cover. In most cases, 10,000-20,000 forb seeds per acre should result in a noticeable forb component, as long as grass seeding rates do not exceed those recommended above (R. Henderson, personal communication). Forb seeds vary greatly in size and weight; therefore, an average seeding rate cannot be provided. For more detailed information on seed mixes and seeding rates for native grasses and forbs under differing soil moisture conditions, see Henderson (1995).

Planting a mix of grass species is preferable to planting monocultures, and native grasses are generally preferable to non-native cool-season grasses, although birds do not require them. Native grasses and forbs are also better than non-native species for prairie invertebrates (Henderson and Sample 1995). However, there may be specific cases where monocultures can be used, such as targeting habitat for sedge wren or Henslow's sparrow.

Restorations of native grasslands should be targeted for areas in the state that were grasslands in presettlement times (Henderson and Sample 1995).

Water-Level Manipulations
Water-level manipulations can be a critical tool—often used in conjunction with other management practices such as burning—in maintaining wet grasslands and sedge meadows. A lowered water table, caused by on-site or nearby ditching or drainage, can result in dry conditions and encourage succession to shrub carr or tree-dominated communities. Alternatively, deep flooding can replace the sedge meadows or other wet grassland habitats with open water or emergent marshes that are of little value to grassland birds (Mossman and Sample 1990).

Conventional Cropping Practices
The use of traditional agricultural crops—row crops, small grains, and legume hay—by grassland birds can be seen in Table 1.

• Row crops have the lowest value for grassland birds, although many bird species forage in row-crop fields. Corn is also an important winter food resource for resident species such as pheasant, turkey, bobwhite quail, and sometimes prairie-chicken. Vesper sparrow is the only species of management concern that regularly nests in row crops, and most of its nests are destroyed by farm machinery or predators in those fields (Rodenhouse and Best 1983). Habitat quality is improved by reducing the number of passes that farm machinery makes through crop fields or by increasing the interval between passes to at least 3.5 weeks to allow time for a typical passerine grassland bird nesting cycle (Stallman and Best 1996).

• Small grains receive low to moderate use by grassland birds (nesting species include red-winged blackbird, bobolink, horned lark, and vesper and savannah sparrow), but unlike hayfields they are harvested late enough to avoid the peak nesting season. Also, they appear to be suitable adjacent habitats or buffers in agricultural landscapes.

• Although alfalfa hay attracts many species, it is typically a valuable habitat only for very early nesters such as vesper sparrow and red-winged blackbird unless harvesting is delayed, in which case later nesters such as dickcissel can successfully fledge young. Otherwise it functions largely as an ecological trap.

• Some grass or mixed grass and legume hay is typically harvested late enough in July to allow for successful nesting by grassland birds.

• Contour strip-cropping is commonly practiced to reduce soil erosion, especially in the Southwestern Upland. While grassland bird abundance can be higher in strip crops than on normal fields for some species, such as bobolink, eastern meadowlark, and vesper and grasshopper sparrow (Good and Dambach 1943), it may not be higher for other species. Also, nest productivity and predation rates in strip crops compared to conventional fields are not known.

Virtually all of Wisconsin's historical prairie acreage has been converted to cropland. The primary row crop in the state is corn, which has increased in recent decades due to the conversion of pasture and small grains. Vesper sparrow, horned lark, and killdeer are the only species that commonly nest in corn.

The most valuable agricultural habitats for grassland birds are old fields, lightly to moderately grazed pastures, fallow fields, wet meadows (undisturbed or periodically cropped or grazed fields), and late-cut grass hay and mixed grass and legume hay. None of these habitats is as common as those described above.

Cropping systems that reduce pesticide and inorganic fertilizer use—such as through integrated pest management and measuring soil requirements, respectively—are preferred over systems that depend heavily on these chemicals. Both inorganic fertilizers and pesticides reduce the invertebrate food base and may negatively affect young or adult birds. Pesticides can also simplify the vegetation structure and plant species composition in crop fields (Rodenhouse et al. 1995).

Contour strip-cropping in Iowa County. Contour strips are a common erosion control practice in the hilly Driftless Area (Southwestern Upland Natural Division).

Raking hay in Dane County. Early harvest of alfalfa hay can cause high mortality for grassland birds.

Alternative Cropping Practices
Organic farming.  Organic farming has many advantages over conventional farming for grassland birds. It provides better nesting habitat (Ducey and Miller 1980, Gremaud 1983) and may have better food resources due to decreased use of insecticides and increased soil organic matter. However, organic farms tend to have smaller fields than conventional farms (Ducey and Miller 1980) and may thus fail to meet minimum area requirements. Because they have small field sizes, organic farms tend to have more edge habitats than conventional farms, which increases the negative edge effects of nest predation and parasitism. Organic farms may also rely heavily on mechanical cultivation for weed control, which can result in the destruction of nests.

Conservation tillage.  Conservation tillage has been shown to provide better nesting habitat for more grassland bird species than conventionally tilled fields (Warburton and Klimstra 1984, Basore et al. 1986). The presence of crop residue on the soil surface also supports higher numbers of invertebrates than conventionally tilled fields, therefore increasing food resources. However, increased mechanical cultivation and possibly pesticide use for weed control in conservation tillage fields may cause them to be ecological traps (Best 1986). Conservation tillage systems that reduce the need for additional pesticide use, such as ridge-till or the use of integrated pest management, are preferred for row crop grassland bird habitat.

Intensive rotational grazing.  This increasingly popular practice (Undersander et al. 1991) is not beneficial to most grassland bird species because of intensive trampling from cattle and short rest periods between grazing events (Paine et al. 1996a, Temple et al. n.d,). However, when incorporated into farms with adjacent grasslands that are not cut or grazed until after the peak breeding season, rotational grazing may boost overall grassland bird productivity above that of conventional farms (Temple et al. n.d.).

Alternative Crops.  At present, few alternative crops have been produced in large enough areas in Wisconsin to assess their value as grassland bird habitat. In Iowa, experimental strip intercropping of corn, soybeans, oats, and legumes produces higher bird abundance than conventional row crops but may function as an ecological trap by attracting birds to settle in a habitat with a low rate of nest success (Stallman and Best 1996). Native warm-season grasses grown as biomass energy crops can improve grassland bird diversity compared to conventional row crops (Paine et al. 1996b). Research on other crops and cropping practices that are both beneficial to farmers and birds is currently being conducted.

Set-Asides
Set-asides are agricultural fields taken out of crop production for some economic or conservation purpose as part of a USDA program. Current agricultural policy is changing the status of set-aside programs.

Annual set-asides.  Annual set-asides, such as Acreage Conservation Reserve (ACR) fields enrolled in the now-defunct USDA Feed Grain Program, received moderate use from grassland birds of management concern (Sample 1995) and provided higher quality habitat than row crops. Some set-aside fields such as those planted to small grains suffered because regulations allowed for late planting during the breeding season, while others such as grass and legume mixtures suffered from early mowing. Although annual set-aside programs are currently being phased out, grassland birds will benefit in the future more from multi-year programs that encourage diverse plantings of grasses and forbs and that do not release such plantings for cutting before 15 July. Bird communities in annual set-asides are similar to those listed in Appendix E and Table 1, under alfalfa hay, small grains, and fallow fields.

Long-term set-asides.  Habitat established under programs such as the CRP has proven to be valuable to grassland birds in Wisconsin. In CRP fields in the southern part of the state, several species of management concern, including dickcissel, vesper and grasshopper sparrow, bobolink, and western meadowlark have been found in similar densities to those in other preferred habitats (Sample 1995). Early release of CRP fields for haying due to drought conditions during the bird breeding season and emphasis on seed mixtures aimed at the creation of tall, dense cover, however, have limited the CRP's value for grassland birds. We make the following recommendations for improving habitat quality in long-term set asides such as CRP land:

• Include native forbs in seed mixes, typically enough to provide 10% cover of forbs (see planting and restoration recommendations above).

• Include grasses of varying heights in seed mixes to promote a variety of height and density among fields. For example, be sure to provide some seed mixes featuring short native grasses (e.g., little bluestem, side-oats grama, prairie dropseed, and Scribner's panicum) or short non-native grasses (e.g., Kentucky bluegrass and redtop).

• Reduce grass seeding rates by up to 50% (down to 4-6 lb per acre for cool-season grasses and 3-5 lb per acre for warm-season grasses) to reduce vegetation density and to encourage forbs.

• Allow mowing only after 15 July.

• Allow for management over time to control woody vegetation and rejuvenate the planting (e.g., burning, grazing, late season haying, re-seeding).

• Consider allowing light grazing to reduce vegetation height and density.

• Encourage enrollment of whole fields to avoid linear-shaped fields with high edge:interior ratios.

• Locate other suitable grassland habitat adjacent to set-aside fields when possible.

Firebreaks.  Wide (440 yd), herbaceous (or heath-dominated) firebreaks in the northern forest provide grassland bird habitat and may even serve as important corridors between grassland openings, such as in the barrens area of northwestern Wisconsin. Many grassland species, including sharp-tailed grouse, use such firebreaks (Gregg 1987, Niemuth 1995).

Conifer plantations.  Young conifer plantations are most useful to grassland bird populations when the trees are less than 10 ft tall. Avoid locating these plantations in open grassland landscapes. Typical bird communities of young conifer plantations are listed in Table 1.

Many CRP fields, such as this one in Rock County, have a very dense, homogeneous vegetation structure. While these types of fields are used by some grassland birds, lighter grass seedings with a forb component create a more diverse structure that would benefit more bird species.

 Horned lark

 Bobolink

Vesper sparrow

Northern harrier

Killdeer