Assessing the influence of wind turbines and land-use on mortality risk of avian species on the Llano Estacado with emphasis on birds of prey
Linner, Kristen Marie
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Wind energy is a burgeoning industry on the Llano Estacado of Texas and could negatively affect the local avian community if birds collide with turbines or avoid previously occupied habitat. The purpose of my thesis was to explore the relationship between wind energy, land-use, and bird populations on the Llano Estacado. I assessed the potential effects of wind energy development on three aspects of avian ecology. First, I conducted small-scale point count surveys during the breeding season as well as broad-scale year-round point counts to compare avian diversity and species abundance one year before, and two years after, wind turbine construction. Breeding bird diversity differed significantly among my three years of study (November 2011-August 2014) but I could not attribute this variation to turbine construction. Rather, evidence suggested breeding diversity may be best explained by inter-annual variation of weather patterns on the study area. Diversity also differed significantly across years for broad scale point counts. Additionally, most species and most seasons (e.g, Winter, Spring, Summer, Fall) showed significant differences in abundance across study years, but many of these differences may also be best explained by interannual variation in weather conditions. Second, I surveyed raptors along a 154 km transect each month for one year to evaluate raptor resource selection of local land-use types (cotton, grain agriculture, rangeland, non-grazed grassland) to assess which land-use types may present higher or lower collision risk for raptors. My results indicated species-specific and season-specific patterns were apparent. Species did not use the land-use categories in proportion to availability on the study area. Generally, non-grazed grasslands were used at a greater proportion than expected and cotton agriculture was used less than expected based on availability on the landscape. Third, I studied the breeding ecology of the American Kestrel (Falco sparverius). Specifically, I assessed kestrel nest selection in relation to proximity of five wind turbines located at the Reese Technology Center in Lubbock County, Texas. American Kestrels readily accepted and successfully nested in newly installed nest boxes. Interestingly, 4 of 10 nesting pairs (40%) across two years produced double broods, which is uncommon for the species. The results from my proximity analysis suggested kestrels did not have an affinity for, or an avoidance of, recently constructed wind turbines. My results suggest that overall avian risk from small-scale turbine construction may be difficult to discern due to the effects of weather. Additionally, my results show that raptor-turbine collision risk may be higher if turbines are constructed on non-grazed grassland and lower when turbines are constructed on cotton fields.