Reproductive ecology of greater prairie-chickens and thermal effects of an exotic broadleaf plant

In the Great Plains of North America, more than 70% of historical grasslands have been lost, and remaining grasslands continue to face fragmentation and changes in prevailing land management practices. These changes have important implications for wildlife, especially when they alter the structure and landscape-scale configuration of vegetation. One important way that vegetation influences wildlife is through the modification of temperatures near the ground. We examined the impact of the invasive species sericea lespedeza (Lespedeza cuneata) on the near-ground thermal environment in a tallgrass prairie. Temperatures were significantly cooler when sericea was present than when it was absent. While increasing sericea cover did not significantly affect spatial thermal variation, it did have a quadratic relationship with temporal thermal variation, indicating that thermal variation across the diel cycle was lowest when sericea cover was moderate. At broader spatial scales, we investigated whether the configuration of burn patches on the landscape influenced nest and brood survival of greater prairie-chickens (Tympanuchus cupido pinnatus). Although we did not detect any significant relationships between proximity to burn edges, tree cover, or water sources and nest or brood success, nest survival was negatively related to wetter conditions during the nesting season. Brood survival during the first week post-hatch was negatively related to wetter conditions two years previously and negatively related to increasing daily path sinuosity. When we examined survival for individual chicks rather than brood survival, we found that survival probability between Days 1 and 4 post-hatch was influenced by proximity to burn edges. Survival probability was highest for chicks that hatched from nests 300-500 m from the nearest recent burn or that remained 0-300 m on average from the nearest recent burn. We also found support for litter depth as a potential mechanism underlying these relationships, as early chick survival was negatively related to litter depth. This suggests that the farther chicks must travel through unburned, accumulated vegetation, the more difficult it is for them to escape predators or capture prey. Our findings highlight how changes in plant communities and vegetation structure affect both the abiotic environment and wildlife populations in the tallgrass prairie.