Restored Heterogeneity as a Conservation Strategy for Grassland Birds

Grasslands are inherently dynamic in space and time evolving with frequent disturbance from fire and herbivores. Throughout much of the world, grasslands have been converted and fragmented and many remaining grasslands have become homogenous as a consequence of human actions. As a result, ecosystem function has declined and biodiversity loss has led to decreased ecological services. Of particular concern are highly imperiled grassland birds which have experienced greater population declines than any other habitat associated guild of birds in North America. Conservation efforts that restore heterogeneity to grasslands through the re-coupling of fire and grazing may be an effective strategy for stabilizing or increasing grassland bird populations. We examined Greater Prairie-Chicken (Tympanuchus cupido) ecology, breeding bird community diversity and stability, and non-breeding bird community diversity and patch occupancy in tallgrass prairie with restored structural and compositional heterogeneity. We found that Greater Prairie-Chickens selected for patches with greater time since fire and grazing and that taller vegetation increased nest survival. Additionally, nests that survived were in cooler environments and prairie-chickens displayed fine scale thermal habitat selection as nest sites were nearly 4˚C cooler than micro-sites within 2 meters of nests. We found that heterogeneity increased breeding bird community diversity and that increased heterogeneity resulted in greater community stability over time. Finally, non-breeding bird community diversity increased as a result of structural heterogeneity and occupancy modeling revealed that certain species selected for varying patches along a disturbance gradient (i.e, recently disturbed to relatively undisturbed) that resulted from fire and grazing dependent heterogeneity. Our findings add to a growing body of literature supporting the use of fire and grazing to create a shifting grassland mosaic that increases vegetation structural and compositional heterogeneity and maximizes native biodiversity within rangeland ecosystems through the conservation of natural patterns and processes. Additionally, these data provide evidence that variation in grassland structure resulting from the fire-grazing interaction may be important in moderating thermal environments and highlights the complex and interactive effects of restored ecological processes on ecosystems. We recommend future management efforts in rangelands focus on restored disturbance process to increase heterogeneity and improve grassland bird conservation.Natural Resources and Ecology Managemen