Der Beitrag von Kollisionsopfersuchen zur Abschätzung des Kollisionsrisikos von Fledermäusen an Windenergieanlagen

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Estimating Bat and Bird Mortality Occurring at Wind Energy Turbines from Covariates and Carcass Searches Using Mixture Models

Environmental impacts of wind energy facilities increasingly cause concern, a central issue being bats and birds killed by rotor blades. Two approaches have been employed to assess collision rates: carcass searches and surveys of animals prone to collisions. Carcass searches can provide an estimate for the actual number of animals being killed but they offer little information on the relation between collision rates and, for example, weather parameters due to the time of death not being precisely known. In contrast, a density index of animals exposed to collision is sufficient to analyse the parameters influencing the collision rate. However, quantification of the collision rate from animal density indices (e.g. acoustic bat activity or bird migration traffic rates) remains difficult. We combine carcass search data with animal density indices in a mixture model to investigate collision rates. In a simulation study we show that the collision rates estimated by our model were at least as precise as conventional estimates based solely on carcass search data. Furthermore, if certain conditions are met, the model can be used to predict the collision rate from density indices alone, without data from carcass searches. This can reduce the time and effort required to estimate collision rates. We applied the model to bat carcass search data obtained at 30 wind turbines in 15 wind facilities in Germany. We used acoustic bat activity and wind speed as predictors for the collision rate. The model estimates correlated well with conventional estimators. Our model can be used to predict the average collision rate. It enables an analysis of the effect of parameters such as rotor diameter or turbine type on the collision rate. The model can also be used in turbine-specific curtailment algorithms that predict the collision rate and reduce this rate with a minimal loss of energy production.German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety/FKZ 0327638 A,

Wind farm facilities in Germany kill noctule bats from near and far

Over recent years, it became widely accepted that alternative, renewable energy may come at some risk for wildlife, for example, when wind turbines cause large numbers of bat fatalities. To better assess likely populations effects of wind turbine related wildlife fatalities, we studied the geographical origin of the most common bat species found dead below German wind turbines, the noctule bat (Nyctalus noctula). We measured stable isotope ratios of non-exchangeable hydrogen in fur keratin to separate migrants from local individuals, used a linear mixed-effects model to identify temporal, spatial and biological factors explaining the variance in measured stable isotope ratios and determined the geographical breeding provenance of killed migrants using isoscape origin models. We found that 72% of noctule bat casualties (n = 136) were of local origin, while 28% were long-distance migrants. These findings highlight that bat fatalities at German wind turbines may affect both local and distant populations. Our results indicated a sex and age-specific vulnerability of bats towards lethal accidents at turbines, i.e. a relatively high proportion of killed females were recorded among migratory individuals, whereas more juveniles than adults were recorded among killed bats of local origin. Migratory noctule bats were found to originate from distant populations in the Northeastern parts of Europe. The large catchment areas of German wind turbines and high vulnerability of female and juvenile noctule bats call for immediate action to reduce the negative cross-boundary effects of bat fatalities at wind turbines on local and distant populations. Further, our study highlights the importance of implementing effective mitigation measures and developing species and scale-specific conservation approaches on both national and international levels to protect source populations of bats. The efficacy of local compensatory measures appears doubtful, at least for migrant noctule bats, considering the large geographical catchment areas of German wind turbines for this species

Reduktion des Kollisionsrisikos von Fledermäusen an Onshore-Windenergieanlagen (RENEBAT II)

Fledermausschlagopfer an Windenergieanlagen (WEA) treten an vielen Standorten und teilweise in erheblichen Zahlen auf. Eine Reduktion der Schlagopferzahlen ist aus artenschutzrechtlichen Gründen unverzichtbar und auch für die Akzeptanz des Ausbaus der Windenergie wichtig. Im vorangegangenen Forschungsvorhaben RENEBAT I wurde eine Methode entwickelt, mit der das Schlagrisiko für Fledermäuse an WEA quantifiziert und über anlagenspezifische Betriebsalgorithmen reduziert werden kann. Zentrale Ziele des Forschungsvorhabens RENEBAT II waren die Validierung und Weiterentwicklung der fledermausfreundlichen Betriebsalgorithmen. Getestet wurde der fledermausfreundliche Betrieb an 16 WEA in 8 Windparks (2 WEA je Windpark) in mehreren Naturräumen im Bundesgebiet. Dieser Praxistest konnte zeigen, dass die in RENEBAT I entwickelten statistischen Modelle die Schlagopferzahlen an den untersuchten Anlagen mit hoher Genauigkeit voraussagen können und, dass der fledermausfreundliche Betriebsalgorithmus dazu geeignet ist, das Schlagrisiko mit hoher Präzision auf einen festgelegten Wert des verbleibenden Kollisionsrisikos zu reduzieren. Die Kosten für dieses Vorgehen konnten beispielhaft ermittelt werden. Ein weiteres wichtiges Ziel war die Integration der Forschungsergebnisse in die Planungspraxis. Als Handreichungen für die Praxis wurden daher ein Leitfaden für eine akustische Gondelerfassung an WEA und ein Statistiktool zur Berechnung der tatsächlichen Schlagopferzahl aus der Anzahl gefundener toter Fledermäuse entwickelt. Außerdem wurden die Regelwerke und Empfehlungen einzelner Bundesländer zur Berücksichtigung von Fledermäusen beim Bau und Betrieb von WEA zusammengefasst. Darüber hinaus wurden neue Ansätze zur Verbesserung und Vereinfachung der Erfassung von Fledermäusen an WEA entwickelt und erprobt. Ein Detektorsystem wurde neu entwickelt, das sich als wenig anfällig gegenüber Störgeräuschen erwies und in der Lage war mit hoher Empfindlichkeit und sehr selektiv Fledermausrufe aufzuzeichnen. Um mit verschiedenen Detektorsystemen erfasste Daten miteinander vergleichen zu können, wurde ein Laboraufbau entwickelt, mit dem verschiedene Aspekte der Detektortechnik standardisiert und reproduzierbar untersucht werden können. Der Einsatz eines Helligkeitssensors konnte keine eindeutige Korrelation zwischen der Helligkeit in der Nacht und der Aktivität von Fledermäusen an WEA zeigen. Durch die Messung der Fledermausaktivität mittels 3D-Wärmebilderfassung konnte der erste überzeugende Nachweis geführt werden, dass WEA einen anziehenden Effekt auf Fledermäuse haben. Dies ermöglichte auch die Berechnung von Skalierungsfaktoren für die Berechnung des Schlagrisikos an WEA mit verschiedenen Rotordurchmessern.Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit/0327638C+

A Triple-Isotope Approach to Predict the Breeding Origins of European Bats

Despite a commitment by the European Union to protect its migratory bat populations, conservation efforts are hindered by a poor understanding of bat migratory strategies and connectivity between breeding and wintering grounds. Traditional methods like mark-recapture are ineffective to study broad-scale bat migratory patterns. Stable hydrogen isotopes (δD) have been proven useful in establishing spatial migratory connectivity of animal populations. Before applying this tool, the method was calibrated using bat samples of known origin. Here we established the potential of δD as a robust geographical tracer of breeding origins of European bats by measuring δD in hair of five sedentary bat species from 45 locations throughout Europe. The δD of bat hair strongly correlated with well-established spatial isotopic patterns in mean annual precipitation in Europe, and therefore was highly correlated with latitude. We calculated a linear mixed-effects model, with species as random effect, linking δD of bat hair to precipitation δD of the areas of hair growth. This model can be used to predict breeding origins of European migrating bats. We used δ13C and δ15N to discriminate among potential origins of bats, and found that these isotopes can be used as variables to further refine origin predictions. A triple-isotope approach could thereby pinpoint populations or subpopulations that have distinct origins. Our results further corroborated stable isotope analysis as a powerful method to delineate animal migrations in Europe

Notation of parameters, variables and indices.

<p>Notation of parameters, variables and indices.</p

Estimated number of collisions for each turbine in the two data sets (2007 and 2008) based on the one- and three-level observation model vs. the conventional “corrected count” estimate.

<p>Segments give the 95% credible intervals. The dotted line indicates perfect coincidence.</p

Observed frequencies of the numbers of carcasses found per search in the 2008 data set compared to the ones predicted from our two models (see text).

<p>The ranges are 95% prediction intervals for the model predictions.</p

Parameter estimates (mean and 95% credible interval) for our two models (see text) fitted to different data sets (2007, 2008), and the mortality estimates (mean and range of the total number of collisions at all turbines during n nights) based both on the model (second last column), and on the conventional “corrected count” method.

<p>Parameter estimates (mean and 95% credible interval) for our two models (see text) fitted to different data sets (2007, 2008), and the mortality estimates (mean and range of the total number of collisions at all turbines during n nights) based both on the model (second last column), and on the conventional “corrected count” method.</p

Ratio of the estimated and the true number of collisions per turbine for 50 simulated data sets.

<p>17 turbines were used to fit the model (1700 data points for each box, left panels), collisions were then predicted for a new turbine not used to fit the model (50 data points for each box, right panels). The y-axis is log-scaled so that equivalent proportional increases and decreases result in the same change on the y-axis. Grey boxes indicate model estimates using the one- (upper panels) and three-level (lower panels) observation model (see text). White boxes give the conventional “corrected count” estimates (see text) using only carcass count data and estimates for carcass detection probability. The data has been simulated for two settings with different sample sizes (100 and 300 nights per turbine). The average total numbers of collisions per turbine for these two settings were 4.5 and 14.2 bats respectively. Bold horizontal line = median, box = 50% range of the data, whiskers = last value within 1.5 times the interquartile range, circles = data points further away.</p