Landscape-scale greater prairie-chicken–habitat relations and the Conservation Reserve Program

Both the abundance of greater prairie-chickens (Tympanuchus cupido pinnatus) and the area of grassland enrolled in the Conservation Reserve Program (CRP) in northwestern Minnesota, USA, have recently declined. Although wildlife conservation is a stated objective of the CRP, the impact of the CRP on greater prairie-chicken populations has not been quantified. To address that information need, we evaluated the association between greater-prairie chicken lek density (leks/km²), the number of males at leks (males/lek), and CRP enrollments in the context of landscape structure and composition in northwestern Minnesota. Using data from standardized prairie-chicken surveys and land cover in 17 41-km² survey blocks during 2004–2016, we used a mixed-effect model and a layered approach in an information-theoretic framework at multiple spatial scales to identify covariates related to prairie-chicken abundance. At the landscape scale, lek density was best explained by the amount of CRP grassland and wetland, grassland and wetland with long-term conservation goals (state, federal, and The Nature Conservancy owned); other wetlands managed with variable or no continuity in conservation goals; the contiguity of grasslands; and the number of patches of grasslands and wetlands in each survey block each year. Increasing the amount of CRP grassland in 41-km² survey blocks by 1 km² (2.4%) resulted in a corresponding increase of 6% in lek density. At the lek scale, the number of males per lek was best explained by the amount of CRP grassland and other grassland, CRP wetland and other wetland, forests, developed areas, shrubland, and the contiguity of CRP grassland. Increasing the amount of CRP grassland in the 2-km breeding-cycle habitat radius around a lek by 25% (3 km²) corresponded to a 5% increase in males per lek. Our results suggest that both increasing the quantity of grassland CRP and wetland CRP enrollments and aggregating CRP grassland enrollments may increase greater prairie-chicken abundance. © 2019 The Wildlife Society.     

Weather Influences Multiple Components of Greater Prairie-Chicken Reproduction

The influence of weather on wildlife populations has been documented for many species; however, much of the current literature has focused on the effects of weather within a season and consists of short-term studies. The use of long-term datasets that cover a variety of environmental conditions will be essential for assessing possible carry-over effects of weather experienced in one season on behavior and fitness in subsequent seasons. In this study, we evaluated the effects of weather variables measured over multiple temporal scales on the reproductive performance and behavior of greater prairie-chickens (Tympanuchus cupido) in Osage County, Oklahoma, USA, from 2011–2019. Considering weather over a range of temporal extents allowed us to determine the relative importance of short-term weather events, such as daily temperature and precipitation, versus more chronic shifts in weather such as persistent drought on the reproductive performance of greater prairie-chickens. We used an information-theoretic model building approach to develop models describing the effects of daily weather variables and drought conditions on daily nest survival, nest incubation start dates, and clutch size. Daily nest survival was primarily influenced by conditions experienced during incubation with daily nest success declining in years with wetter than average springs and during extreme precipitation events. Daily nest survival also declined under higher maximum daily temperatures, especially in years with below-average rainfall. Greater prairie-chickens began nesting earlier and had smaller clutch sizes for initial nests and renests in years with warmer temperatures prior to the nesting season. Additionally, incubation of nests started later in drought years, indicating carry-over effects in greater prairie-chicken reproductive behaviors. Our work shows that if the weather in the Great Plains becomes more variable, with increasing frequency of drought and extreme precipitation events, wildlife species that inhabit these grassland landscapes will likely experience changes in reproduction, potentially influencing future populations. © 2020 The Wildlife Society.     

Using regional wildlife surveys to assess the CRP: scale and data-quality issues

ABSTRACT.   Evidence that the Conservation Reserve Program (CRP) has resulted in large-scale increases in populations of grassland birds is limited. Detecting large-scale CRP effects is difficult because agricultural landscapes are complex, dynamic systems where many concurrent changes are occurring across space and time, and CRP is only one of many factors influencing wildlife populations. Trying to isolate and quantify the contribution of CRP to large-scale population changes under these conditions is extremely difficult and tenuous. Data-quality issues affecting many large-scale monitoring programs exacerbate the problem. We use a case study of land-use and pheasant-monitoring data in Minnesota from 1974–1997 to illustrate these problems. In our example, roadside counts of Ring-necked Pheasants ( Phasianus colchicus ) were correlated positively with percent of CRP grasslands within 1.6 km of survey routes, but the predicted change in mean pheasant counts (pre-CRP vs. CRP) was negative in three of five regions despite the addition of up to 8% CRP grasslands. We also documented concurrent losses (1.8%–6.1% per year) of alternative reproductive habitats that apparently counteracted the positive association between pheasant counts and CRP abundance. These results illustrate the need for a more comprehensive evaluation of Farm Bill effects on wildlife, including commodity provisions that lead to conversion of pasture, hayland, and small grains to row crops.     

Effects of rangeland management on the site occupancy dynamics of prairie-chickens in a protected prairie preserve

We investigated the site occupancy dynamics of greater prairie-chickens at Konza Prairie Biological Station, a protected site in northeastern Kansas that is managed for ecological research. We surveyed the site during mid-Mar to mid-May, 1981–2008, and recorded detections of birds in a grid of 6.3 ha survey plots (n = 187 plots). We used multiseason occupancy models to estimate the probabilities of occupancy (ψ) and detection (p), and tested whether land cover in woody vegetation, and land use with prescribed fire or grazing management influenced the dynamic processes of site colonization and local extinction. Probability of detection per site was consistently <1 and varied among years (p = 0.12–0.82). Site occupancy of prairie-chickens declined 40% over the study period from a high of ψ = 0.19 ± 0.02 SE in 1981 to a low of 0.11 ± 0.03 in 2008, despite protection from disturbance at leks and losses to harvest. We found that different sets of environmental factors impacted the probabilities of colonization and local extinction. Probability of colonization for an unoccupied site was negatively associated with the proportion of site occupied by woodland cover (β = −1.25), and was lower for grazed sites (β = −0.62). In contrast, probability of local extinction was affected by a weak interaction between grazing and average frequency of prescribed fire (β = −1.01), but model-averaged slope coefficients were not statistically different than 0. To conserve prairie-chickens, we recommend prairies be managed with combinations of prescribed fire and grazing that maintain a heterogeneous mosaic of prairie habitats, while preventing woody encroachment. To assess biotic responses to land management practices, field sampling should be based on occupancy models or similar techniques that account for imperfect detection. © 2011 The Wildlife Society.     

Dispersion of greater prairie chicken nests in relation to lek location: evaluation of the hot-spot hypothesis of lek evolution

The hot-spot hypothesis suggests that males should establishleks in areas where they are more likely to encounter females;these areas are determined, in part, by overlap in home rangesof females. We examined this hypothesis using data on movementof greater prairie chickens (Tympanuchus cupido) in northeasternColorado during 1986–1988. The relative quality of variouslocations as potential lek sites was estimated using nest-to-lekdistances of females; quality (male breeding potential) wasevaluated on a scale of 0 to 1 and was positively correlatedwith proximity to nest sites of females. Monte Carlo simulationswere conducted to examine male breeding potential under varyingconditions of observed and random lek locations. Male breedingpotential was higher at actual lek sites than at random leksites. Distributions of leks and nests supported predictionsof the hot-spot hypothesis.     

Mixed responses of farmland birds to the Conservation Reserve Enhancement Program in Pennsylvania

The Pennsylvania Conservation Reserve Enhancement Program (CREP) was initiated in 2000 and within 4 years, 40,000 ha of conservation grasslands were established in southern Pennsylvania. We determined whether CREP habitat has benefitted farmland and grassland bird populations during the 10 years since the program began. From 2001 to 2010, bird surveyors conducted road-side point counts in a 20-county area in south-central Pennsylvania. We observed positive CREP effects on the abundances (in 2009–2010) and changes in abundance (from 2001–2002 to 2009–2010) of 5 species, including eastern meadowlark (Sturnella magna); negative CREP effects for 3 species, including vesper sparrow (Pooecetes gramineus); and no CREP effects for 2 species, including grasshopper sparrows (Ammodramus savannarum). We additionally observed changes in the size and direction of the local CREP effects (within 250 m of count locations) depending on the amount of CREP grassland or field cover in the surrounding landscape (within 5,000 m of survey routes). For example, the local CREP effect on the change in abundance of eastern meadowlarks was 15 times greater at points nested within landscapes with 9% CREP cover compared to landscapes with 1% CREP cover, indicating the potential for greater benefits of adding new CREP grasslands to areas with more CREP habitat already in the surrounding area. We conclude that more careful spatial targeting of CREP enrollment could improve the benefits of the program for farmland and grassland bird populations. © The Wildlife Society, 2013     

Cattle grazing in CRP grasslands during the nesting season: effects on avian reproduction

Bird populations in grasslands have experienced declines coinciding with loss and fragmentation of prairies. The United States Department of Agriculture (USDA)-administered Conservation Reserve Program (CRP) is the most extensive grassland restoration program in North America and it has especially benefitted grassland birds. Grazing by domestic cattle has been restricted in CRP during avian nesting seasons despite the potential improvements in structuring habitat for a greater diversity of grassland bird species. Potential negative consequences of grazing in CRP grasslands include trampling of nests by cattle, reductions in nest concealment from predators, and attraction of brood-parasitic brown-headed cowbirds (Molothrus ater). We designed an experiment to test for effects of cattle grazing in CRP fields during the nesting season on nest survival and brood parasitism of 5 bird species that commonly nest in CRP grasslands: mourning dove (Zenaida macroura), grasshopper sparrow (Ammodramus savannarum), dickcissel (Spiza americana), and eastern (Sturnella magna) and western (S. neglecta) meadowlarks. Grazing was implemented during summers 2017 and 2018 on 17 of 36 fields followed by a year of rest on all fields in 2019. Of the 879 nests on grazed fields, only 4 were likely trampled by cattle (vs. 54% of all nests estimated as failing because of depredation). Experimental grazing (grazed vs. ungrazed fields) had variable effects on nest survival and cowbird parasitism among the bird species analyzed. Negative effects of grazing on daily nest survival of dickcissel and meadowlarks were apparent, at least in some years. We found no direct effects of grazing on nest survival of mourning dove or grasshopper sparrow. Probability and intensity (cowbird offspring/nest) of cowbird parasitism in dickcissel nests was higher on grazed versus ungrazed sites but only in conservation practice (CP) CP2 (vs. CP25 fields). Parasitism probability of grasshopper sparrow nests by cowbirds was higher on grazed fields in the 2 years after introduction of cattle in 2017. Greater vegetative concealment around nest sites was associated with reduced cowbird parasitism of meadowlark and grasshopper sparrow nests and higher nest survival for grasshopper sparrows. Reductions in vegetative height caused by longer-term or high-intensity grazing might therefore have negative consequences for some grassland birds by increasing nest site visibility and exposure to cowbird parasitism. Our results indicate that cattle grazing in CRP fields during the nesting season might have some negative effects on reproductive success of some grassland bird species, at least in the short term; however, the potential improvements of structuring habitat to accommodate more grassland bird species and increasing landowner participation in the CRP are considerable.     

Northern bobwhite response to Conservation Reserve Program habitat and landscape attributes

The northern bobwhite (Colinus virginianus; hereafter bobwhite) has experienced substantial population declines in recent decades in the United States, and especially in Maryland and Delaware. The United States Department of Agriculture's Conservation Reserve Program (CRP) could provide additional habitat for bobwhites, leading to an increase in bobwhite abundance. I investigated if bobwhite abundance was related to the percent cover of CRP land and landscape attributes in local landscapes on Maryland's Eastern Shore and Delaware. Observers conducted bobwhite point transect surveys at 113 locations during the breeding seasons of 2006–2007, and I calculated landscape metrics for 500-m radius landscapes centered on each point transect location. Most CRP land in the study landscapes was planted to herbaceous vegetation. Bobwhite abundance was strongly positively associated with percent cover of CRP land in the landscape but was not strongly related to percent cover of agriculture or forest or to landscape patch density. These results suggest that the CRP has created additional habitat for bobwhites in Maryland and Delaware and that landscapes with greater proportions of herbaceous CRP practices support more bobwhites. © 2012 The Wildlife Society.     

Cattle grazing in CRP grasslands during the nesting season: effects on avian abundance and diversity

The Conservation Reserve Program (CRP) is a primary tool for restoring grassland in the United States, in part as wildlife habitat, which has benefited declining grassland bird populations. Among potential mid-contract management practices used to maintain early-successional CRP grasslands, cattle grazing had been prohibited and is currently disincentivized during the primary nesting season for birds (much of the growing season), despite the important role that large herbivores historically played in structuring grassland ecosystems. Conservative grazing of CRP grasslands could increase spatial heterogeneity in vegetation structure and plant diversity, potentially supporting higher densities of some grassland bird species and higher bird diversity. Our objective was to determine the effect of experimental cattle grazing on species-specific relative abundance and occupancy, species diversity, and community dissimilarity of grassland birds on CRP grasslands across the longitudinal extent of Kansas, USA (a 63.5-cm precipitation gradient) during the 2017–2019 avian breeding seasons. Fifty-three of 108 fields were grazed by cattle during the growing seasons of 2017 and 2018 and all fields were rested from grazing in 2019. For all analyses, we examined separate model sets for semiarid western versus more mesic eastern Kansas. Using data from line transect surveys, we modeled relative abundances of 5 songbird species: grasshopper sparrow (Ammodramus savannarum), dickcissel (Spiza americana), eastern meadowlark (Sturnella magna), western meadowlark (Sturnella neglecta), and brown-headed cowbird (Molothrus ater). Grazing had delayed yet positive effects on abundances of grasshopper sparrow in western Kansas, and eastern meadowlark in eastern Kansas, but negative effects on dickcissel abundance in western Kansas and especially on burned fields in eastern Kansas. Somewhat counterintuitively, brown-headed cowbirds in western Kansas were more abundant on ungrazed versus grazed fields in the years after grazing began. In addition, we modeled multi-season occupancy of 3 gamebird species (ring-necked pheasant [Phasianus colcicus], northern bobwhite [Colinus virginianus], mourning dove [Zenaida macroura]) and Henslow's sparrow (Centronyx henslowii); grazing did not affect occupancy of these species. In eastern Kansas, species diversity was highest in grazed, unburned fields. In western Kansas, bird communities in grazed and ungrazed fields were dissimilar, as determined from multivariate analysis. Though regionally variable, conservative stocking of cattle on CRP grasslands during the nesting season as a mid-contract management tool might increase bird species diversity by restructuring habitat that accommodates a greater variety of species and decreasing abundances of species associated with taller, denser stands of vegetation.     

Evapotranspiration of annual and perennial biofuel crops in a variable climate

Eddy covariance measurements were made in seven fields in the Midwest USA over 4 years (including the 2012 drought year) to estimate evapotranspiration (ET) of newly established rain‐fed cellulosic and grain biofuel crops. Four of the converted fields had been managed as grasslands under the USDA's Conservation Reserve Program (CRP) for 22 years, and three had been in conventional agriculture (AGR) soybean/corn rotation prior to conversion. In 2009, all sites were planted to no‐till soybean except one CRP grassland that was left unchanged as a reference site; in 2010, three of the former CRP sites and the three former AGR sites were planted to annual (corn) and perennial (switchgrass and mixed‐prairie) grasslands. The annual ET over the 4 years ranged from 45% to 77% (mean = 60%) of the annual precipitation (848–1063 mm; November–October), with the unconverted CRP grassland having the highest ET (622–706 mm). In the fields converted to annual and perennial crops, the annual ET ranged between 480 and 639 mm despite the large variations in growing‐season precipitation and in soil water contents, which had strong effects on regional crop yields. Results suggest that in this humid temperate climate, which represents the US Corn Belt, water use by annual and perennial crops is not greatly different across years with highly variable precipitation and soil water availability. Therefore, large‐scale conversion of row crops to perennial biofuel cropping systems may not strongly alter terrestrial water balances.     

Waterbird Response to Wetlands Restored Through the Conservation Reserve Enhancement Program

Abstract: Conservation programs that facilitate restoration of natural areas on private land are one of the best strategies for recovery of valuable wetland acreage in critical ecoregions of the United States. Wetlands enrolled in the Conservation Reserve Enhancement Program (CREP) provide many ecological functions but may be particularly important as habitat for migrant and resident waterbirds; however, use of, and factors associated with use of, CREP wetlands as stopover and breeding sites have not been evaluated. We surveyed a random sample of CREP wetlands in the Illinois River watershed in 2004 and 2005 to quantify use of restored wetlands by spring migrating and breeding waterbirds. Waterbirds used 75% of wetlands during spring migration. Total use-day abundance for the entire spring migration ranged from 0 to 49,633 per wetland and averaged 6,437 ± 1,887 (SE). Semipermanent wetlands supported the greatest total number of use-days and the greatest number of use-days relative to wetland area. Species richness ranged from 0 to 42 (x̄ = 10.0 ± 1.5 [SE]), and 5 of these species were classified as endangered in Illinois. Density of waterfowl breeding pairs ranged from 0.0 pairs/ha to 16.6 pairs/ha (x̄ = 1.9 ± 0.5 [SE] pairs/ha), and 16 species of wetland birds were identified as local breeders. Density of waterfowl broods ranged from 0.0 broods/ha to 3.6 broods/ha and averaged 0.5 ± 0.1 (SE) broods/ha. We also modeled spring stopover use, waterbird species richness, and waterfowl reproduction in relation to spatial, physical, and floristic characteristics of CREP wetlands. The best approximating models to explain variation in all 3 dependent variables included only the covariate accounting for level of hydrologic management (i.e., none, passive, or active). Active management was associated with 858% greater use-days during spring than sites with only passive water management. Sites where hydrology was passively managed also averaged 402% greater species richness than sites where no hydrologic management was possible. Density of waterfowl broods was 120% greater on passively managed sites than on sites without water management but was 29% less on sites with active compared to passive hydrologic management. Densities of waterfowl broods also were greatest when ratios of open water to cover were 70:30. Models that accounted for vegetation quality and landscape variables ranked lower than models based solely on hydrologic management or vegetation cover in all candidate sets. Although placement and clustering of sites may be critical for maintaining populations of some wetland bird species, these factors appeared to be less important for attracting migrant waterbirds in our study area. In the context of restored CREP wetlands, we suggest the greatest gains in waterbird use and reproduction may be accomplished by emphasizing site-specific restoration efforts related to hydrology and floristic structure. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):654–664; 2008)     

Population Responses of the Northern Bobwhite (Colinus virginianus) to Land Use Changes in the Agricultural Landscapes of Ohio,USA

Population Ecology - Conversion of natural land cover to agriculture is one of the primary threats to biodiversity worldwide. The Conservation Reserve Program (CRP) and woodlot edge enhancement are...     

Influence of conservation reserve program mid-contract management and landscape composition on northern bobwhite in tall fescue monocultures

The United States Department of Agriculture (USDA) authorized mid-contract management (MCM) in 2004 to restore and maintain plant species composition and structural diversity in aging Conservation Reserve Program (CRP) fields for the northern bobwhite (Colinus virginianus) and other grassland-dependent wildlife. We implemented 3 USDA-approved MCM regimes (i.e., strip disking, strip glyphosate spraying, and strip glyphosate spraying in combination with legume interseeding) in 60 tall fescue (Festuca arundinaceae) CRP monocultures in south-central Illinois, USA, during 2005–2008. We hypothesized that adult bobwhite relative densities and brood presence would increase following MCM that effectively restored early successional plant communities in otherwise monotypic stands of tall fescue. We estimated annual adult bobwhite relative densities and brood presence-absence in managed and unmanaged CRP. We modeled vegetation characteristics and landscape composition to identify factors influencing adult densities and brood presence. Adult relative densities were 2-fold greater in managed fields than in unmanaged fields, and were negatively correlated with greater percentages of grass cover. Adult densities were positively correlated with greater plant species diversity, and greater percentages of bare ground and legume cover. Logistic regression and odds ratio estimates indicated that fields managed with glyphosate-interseed and glyphosate treatments were 39.6% more likely to have broods than unmanaged CRP, whereas disked fields were 10.0% more likely than unmanaged CRP. These models indicated that the probability of brood presence was greater in fields with increased percentage of bare ground, greater plant species diversity, and decreased percentage of grass and litter cover. These findings suggest that a 3-year rotation of glyphosate or glyphosate-interseed treatments can enhance habitat conditions for adult bobwhites and broods in CRP tall fescue monocultures. © 2011 The Wildlife Society.