Comparing methods to estimate the proportion of turbine-induced bird and bat mortality in the search area under a road a
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Comparing methods to estimate the proportion of turbine-induced bird and bat mortality in the search area under a road and pad search protocol Joseph Duggan Maurer1 · Manuela Huso2,3 · Daniel Dalthorp2 · Lisa Madsen3 · Claudio Fuentes3 Received: 3 December 2018 / Revised: 2 September 2020 / Accepted: 19 September 2020 / Published online: 30 November 2020 © The Author(s) 2020
Abstract Estimating bird and bat mortality at wind facilities typically involves searching for carcasses on the ground near turbines. Some fraction of carcasses inevitably lie outside the search plots, and accurate mortality estimation requires accounting for those carcasses using models to extrapolate from searched to unsearched areas. Such models should account for variation in carcass density with distance, and ideally also for variation with direction (anisotropy). We compare five methods of accounting for carcasses that land outside the searched area (ratio, weighted distribution, non-parametric, and two generalized linear models (glm)) by simulating spatial arrival patterns and the detection process to mimic observations which result from surveying only, or primarily, roads and pads (R&P) and applying the five methods. Simulations vary R&P configurations, spatial carcass distributions (isotropic and anisotropic), and per turbine fatality rates. Our results suggest that the ratio method is less accurate with higher variation relative to the other four methods which all perform similarly under isotropy. All methods were biased under anisotropy; however, including direction covariates in the glm method substantially reduced bias. In addition to comparing methods of accounting for unsearched areas, we suggest a semiparametric bootstrap to produce confidence-based bounds for the proportion of carcasses that land in the searched area.
Handling Editor: Bryan F. J. Manly
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Joseph Duggan Maurer [email protected], [email protected] Manuela Huso [email protected]
1
W. L. Gore & Associates, 4250 W Kiltie Ln, Flagstaff, AZ 86005, USA
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US Geological Survey, Forest and Rangeland Ecosystem Science Center, 777 NW 9th Street, Suite 400, Corvallis 97330, OR, USA
3
Department of Statistics, Oregon State University, 239 Weniger Hall, Corvallis 97331, OR, USA
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Environmental and Ecological Statistics (2020) 27:769–801
Keywords Density-weighted proportion · Detection bias · R&P · Wildlife mortality · Anisotropy
1 Introduction Impacts to birds (particularly raptors) from collisions with wind turbines have been of concern in the U.S. since the early 1990s (Orloff and Flannery 1992) and impacts to bats since the early-2000s (Kerns and Kerlinger 2004). The magnitude of the impact is typically assessed through post-construction monitoring (PCM) (Howell and DiDonato 1991; Kunz et al. 2007; Arnett et al. 2008; Strickland et al. 2011). PCM to estimate mortality—the total number of turbine-induced bird or bat fatalities occurring over a specified period of time at individual wind projects—typically involves conducting carcass surveys, where hu
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