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Bird collisions at wind turbines in a mountainous area related to bird movement intensities measured by radar
Author: Aschwanden, Janine; et al.
Bird collisions at wind turbines are perceived to be an important conservation issue. To determine mitigation actions such as temporary shutdown of wind turbines when bird movement intensities are high, knowledge of the relationship between the number of birds crossing an area and the number of collisions is essential. Our aim was to combine radar data on bird movement intensities with collision data from a systematic carcass search.
We used a dedicated bird radar, located near a wind farm in a mountainous area, to continuously record bird movement intensities from February to mid-November 2015. In addition, we searched the ground below three wind turbines (Enercon E-82) for carcasses on 85 dates and considered three established correction factors to extrapolate the number of collisions.
The extrapolated number of collisions was 20.7 birds/wind turbine (CI-95%: 14.3–29.6) for 8.5 months. Nocturnally migrating passerines, especially kinglets (Regulus spp.), represented 55% of the fatalities. 2.1% of the birds theoretically exposed to a collision (measured by radar at the height of the wind turbines) were effectively colliding.
Collisions mainly occurred during migration and affected primarily nocturnal migrants. It was not possible to assign the fatalities doubtlessly to events with strong migration. Fresh-looking carcasses were found after nights with both strong and weak bird movement intensities, indicating fatalities are not restricted to mass movement events (onshore). Rather, it is likely that an important factor influencing collision risk is limited visibility due to weather conditions. Local and regional visibility should be considered in future studies and when fine-tuning shutdown systems for wind turbines.
Janine Aschwanden, Herbert Stark, Dieter Peter, Thomas Steuri, Baptiste Schmid, Felix Liechti
Swiss Ornithological Institute, Switzerland
Volume 220, April 2018, Pages 228-236
Author: Infinity Power Partners
Download original document: “Easement for Wind Energy Development: Triple H Wind Project”
Author: Perold, V.; Ralston-Paton, S.; and Ryan, P.
[Abstract] Wind energy is a clean, renewable alternative to fossil fuel-derived energy sources, but many birds are at risk from collisions with wind turbines. We summarise the diversity of birds killed by turbine collisions at 20 wind energy facilities (WEFs) across southwest South Africa. Monitoring from 2014 to 2018 recovered 848 bird carcasses across all WEFs, at a crude rate of 1.0 ± 0.6 birds turbine−1 y−1 at 16 WEFs with at least 12 months of postconstruction monitoring. However, mortality estimates adjusted for detection and scavenger bias were appreciably higher: 4.6 ± 2.9 birds turbine−1 y−1 or 2.0 ± 1.3 birds MW−1 y−1 (n = 14 WEFs with site-specific bias correction factors), which is slightly lower than mean rates reported in the northern hemisphere, but still well within range. A striking result was the high diversity of birds killed: 130 species from 46 families, totalling 30% of bird species recorded at and around WEFs, including some species not recorded by specialist surveys at WEF sites (e.g. flufftails Sarothruridae). Species accumulation models suggest that 184 (±22) species will be killed at these facilities, some 42% of species found in the vicinity of WEFs. This is despite the smaller number of migrants in the study region, compared with the north temperate zone. Diurnal raptors were killed most often (36% of carcasses, 23 species) followed by passerines (30%, 49 species), waterbirds (11%, 24 species), swifts (9%, six species), large terrestrial birds (5%, 10 species), pigeons (4%, six species) and other near passerines (1%, seven species). Species of conservation concern killed include endangered Cape Vultures Gyps coprotheres and Black Harriers Circus maurus, both of which are endemic to southern Africa. Every effort must be made to site wind energy facilities away from important areas for birds, particularly raptors.
V. Perold and P. Ryan, FitzPatrick Institute of African Ornithology, Biological Sciences, University of Cape Town, Cape Town, South Africa
S. Ralston-Paton, BirdLife South Africa, Pinegowrie, South Africa
Ostrich 2020: 1–12. doi: 10.2989/00306525.2020.1770889
Download original document: “On a collision course? The large diversity of birds killed by wind turbines in South Africa”
Mortality limits used in wind energy impact assessment underestimate impacts of wind farms on bird populations
Author: Schippers, Peter; et al.
1. The consequences of bird mortality caused by collisions with wind turbines are increasingly receiving attention. So‐called acceptable mortality limits of populations, that is, those that assume that 1%–5% of additional mortality and the potential biological removal (PBR), provide seemingly clear‐cut methods for establishing the reduction in population viability. 2. We examine how the application of these commonly used mortality limits could affect populations of the Common Starling, Black‐tailed Godwit, Marsh Harrier, Eurasian Spoonbill, White Stork, Common Tern, and White‐tailed Eagle using stochastic density‐independent and density‐dependent Leslie matrix models. 3. Results show that population viability can be very sensitive to proportionally small increases in mortality. Rather than having a negligible effect, we found that a 1% additional mortality in postfledging cohorts of our studied populations resulted in a 2%–24% decrease in the population level after 10 years. Allowing a 5% mortality increase to existing mortality resulted in a 9%–77% reduction in the populations after 10 years.
Peter Schippers, Ralph Buij, Alex Schotman, Jana Verboom, Henk van der Jeugd, Eelke Jongejans
Wageningen Environmental Research, Wageningen University & Research; Environmental Systems Analysis, Wageningen University; Vogeltrekstation – Dutch Centre for Avian Migration and Demography, Wageningen; Animal Ecology and Physiology, Radboud University, Nijmegen, The Netherlands
Ecology and Evolution. Published on line 04 June 2020. doi: 10.1002/ece3.6360
Download original document: “Mortality limits used in wind energy impact assessment underestimate impacts of wind farms on bird populations”