Environmental and socioeconomic concerns have led the U.S. Department of Energy to develop new targets for domestic use of energy resources. Wind energy development is targeted to fulfill 20% of the U.S. energy demand by 2030, a goal that requires a 29-fold increase from the installed capacity in 2007 (Arnett et al. 2007, DOE 2008). The potential effects of wind energy development on wildlife, especially migratory birds and bats, have received increased attention over the past decade (Drewitt and Langston 2006, Arnett et al. 2007, Kuvlesky et al. 2007, Smallwood and Thelander 2008, Pearce-Higgins et al. 2012). A review of published studies estimated that wind turbines and associated infrastructure are responsible for ∼10,000–40,000 bird fatalities per year in the U.S., an average of 2.19 fatalities per year per turbine (Erickson et al. 2001). Direct mortality rates associated with wind energy development may be low and unlikely to affect population viability for most bird species (Osborn et al. 2000), but some taxa may be sensitive and more susceptible to population-level effects (Hunt et al. 1998, Smallwood and Thelander 2008). Indirect effects of wind energy development are poorly understood, but behavioral avoidance, alteration of habitat quality, or changes in trophic interactions might have important implications for population responses to energy development, and could be more pervasive than direct effects of collision mortality (Gill et al. 1996, Leddy et al. 1999, Hoover and Morrison 2005, Devereux et al. 2008, Pruett et al. 2009, Winder et al. 2013).
The Greater Prairie-Chicken (Tympanuchus cupido; hereafter “prairie-chicken”) is an indicator species for tallgrass prairie ecosystems (Poiani et al. 2001, Johnson et al. 2011) and is listed as Vulnerable by the International Union for Conservation of Nature because populations have declined by ∼70% rangewide over the last three decades (Knopf 1994, Svedarsky et al. 2000, BirdLife International 2012). Prairie-chicken populations are declining in the core of their extant range in Kansas due to low rates of nest, brood, and adult survival, which are related to high rates of predation and intensification of land use for cattle production (McNew et al. 2012, Pitman et al. 2012). Prairie-chickens require a mosaic of habitat types for successful reproduction and survival: open sites at relatively high elevations for display arenas used for lekking, dense vegetative cover for concealment during nesting, and areas of intermediate vegetative structure that are rich in forbs for foraging and rearing of broods (Gregory et al. 2011, Johnson et al. 2011, Matthews et al. 2013). Preferred locations for wind energy development in the Great Plains include high ridges and avoid economically valuable croplands, increasing the potential for conflict between wind energy development and an umbrella species of conservation concern.
Quantitative information on the spatial ecology of prairie-chickens is limited, especially with respect to potential responses to energy development and seasonal differences in habitat use (Niemuth 2011, Patten et al. 2011). Recent field studies have shown that Greater Prairie-Chickens, Lesser Prairie-Chickens (T. pallidicinctus) and Greater Sage-Grouse (Centrocercus urophasianus) can be negatively affected by energy development. Proximity to extraction wells, roads, towers, or transmission lines has been linked to abandonment of leks, behavioral avoidance, and loss of nesting habitat (Connelly et al. 2000, Pitman et al. 2005, Pruett et al. 2009, Hagen et al. 2011, Blickley et al. 2012). However, the management implications of the results of past studies cannot be extended to a landscape scale because no study has directly evaluated the role of landscape metrics in spatial interactions between grouse and energy development. Demographic analyses of prairie-chicken populations in Kansas indicate that adult female mortality rates are 3–4 times higher during the 6-month breeding season than the 6-month nonbreeding season (Hagen et al. 2007, Augustine and Sandercock 2011, Winder et al. 2013). However, analyses of demographic rates alone do not allow us to determine whether space use is a driving factor in mortality risk.
Our study is the first application of resource utilization functions (RUFs) to investigate the response of a wildlife population to energy development. RUFs calculate a probabilistic measure of non-uniform space use within an animal's home range, and then use a multiple regression framework to relate space use to resource variables, while accounting for spatial autocorrelation among multiple locations from the same individual. Regression coefficients from the RUF can be used to draw inferences about the direction and magnitude of relationships between intensity of space use and values of selected resources at either an individual or a population level (Marzluff et al. 2004, Kertson et al. 2011). The objectives of our field study were to use resource utilization functions as an improved tool for testing for potential effects of wind energy development on resource use, and for quantifying the breeding and nonbreeding spatial ecology of female prairie-chickens. We collected seasonal movement data on radio-marked females before and after construction of a wind energy facility in the Smoky Hills ecoregion in northcentral Kansas. We developed individual and population level resource utilization functions for four separate periods: the breeding and nonbreeding seasons, both before and after construction of a wind energy facility. We used resource utilization functions to investigate the relationships between prairie-chicken space use and a set of ten landscape metrics describing land cover, patchiness, anthropogenic disturbance, and prairie-chicken social behavior.
We used home range estimates and resource utilization functions to test for three hypothetical effects of wind energy development on space use by prairie-chickens: (1) displacement away from the developed area, (2) expansion of home ranges, or (3) avoidance that leads to changes in space use within home ranges (Fig. 1). If wind energy development decreases habitat quality in developed areas, we predicted that prairie-chickens would shift home ranges or move greater distances to obtain adequate resources for forage, cover, or lek sites (Patten et al. 2011). If wind energy development resulted in behavioral avoidance of impacted areas by female prairie-chickens, we predicted that relative use would have a significant positive relationship with distance to wind turbine. Females require cover for nesting and brood-rearing (McNew et al. 2013), and habitat requirements for foraging and roosting may differ during the nonbreeding season. The results of our field study provide new insights into the quantitative spatial ecology of prairie-chickens in response to energy development, and can be used to improve management and conservation efforts for prairie grouse.