Abstract
Advancements in wind turbine technology have led to larger, more energy productive turbines. However, the degree to which increases in turbine size may affect wildlife mortality is not yet understood. We developed a Bayesian hierarchical model to investigate the potential influence of three turbine size parameters (ground clearance, rotor diameter, and power rating) on fatality rates and fall distances of three representative species: hoary bat (Lasiurus cinereus), horned lark (Eremophila alpestris), and red-tailed hawk (Buteo jamaicensis). Our model incorporated a paired design to isolate turbine size effects, assuming turbines monitored in the same year and in close proximity were similarly influenced by random effects such as weather and habitat. We used Integrated Population Integral Projection Modeling to analyze four component datasets (searcher efficiency, carcass persistence, fatality rates, and fall distributions) derived from focal and priors datasets. Our model showed generally consistent and well-mixed results despite its size and complexity. Decreasing ground clearance led to increased fatality rates for all three species and was most pronounced for hoary bats; increased rotor diameter led to increased fatality rates for red-tailed hawks and for horned larks to a lesser extent. Increasing power capacity led to increased horned lark fatality rates, with a weaker influence on red-tailed hawks. Turbine size covariates had strong species-specific effects on fall distributions with implications for selecting search plot dimensions and analyzing fatality estimates in future studies. To our knowledge, this is the first investigation of ground-clearance effects on fatality rates and of turbine size parameters on carcass fall distributions.