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Um den Fledermausschlag an Windenergieanlagen (WEA) zu reduzieren, wird der Betrieb von WEA in Zeiten hoher Fledermausaktivität gedrosselt. Da das hierfür notwendige Regelwerk erst ungefähr 2011 etabliert wurde, laufen alte WEA, d.h. 75 % der aktuellen WEA auf dem deutschen Festland, ohne derartige Betriebssteuerungen zum Fledermausschutz. Wir ermittelten für einen alten Windpark, der im Jahr 2001 in einem ackerbaulich geprägten Umfeld ohne höhere Vegetation installiert wurde, wie viele Schlagopfer an alten WEA potenziell generiert werden. Bei systematischen Schlagopfersuchen konnten wir im August und September 37 Schlagopfer finden. Ein Experiment zur Bestimmung der Kadaverabtragrate zeigte, dass 95 % aller Kadaver innerhalb von 24 Stunden abgetragen wurden. Unter Berücksichtigung der Kadaverabtragrate und der Sucheffizienz schätzten wir, dass mehrere Hundert Fledermäuse im zweimonatigen Zeitraum an den zwei WEA getötet wurden. Aus Vergleichsgründen führten wir identische Untersuchungen an einem neueren Windpark, der mit Betriebssteuerung zum Fledermausschutz betrieben wird, durch. An diesem vegetationsreichen Standort fanden wir im selben Zeitraum keine Schlagopfer an den WEA. Unsere Untersuchung unterstreicht, dass alte WEA ohne Betriebssteuerungen selbst an Offenlandstandorten hohe Schlagopferzahlen generieren können. Hingegen können Betriebssteuerungen an WEA das Schlagrisiko reduzieren selbst wenn diese sich an vegetationsreichen Standorten mit einer erwartungsgemäß hohen Aktivität von Fledermäusen befinden. Die Einführung einer Betriebssteuerung zum Fledermausschutz sollte an Altanlagen möglichst umgehend erfolgen, um die Bestandstückgänge der Kollisionsarten aufzuhalten., Korrespondenz: Christian C. Voigt Leibniz-Institut für Zoo- und Wildtierforschung Berlin, Alfred-Kowalke-Str. 17, 10315 Berlin Tel: +49-30-5168-511 E-Mail: voigt@izw-berlin.de

In late summer, migratory bats of the temperate zone face the challenge of accomplishing two energy-demanding tasks almost at the same time: migration and mating. Both require information and involve search efforts, such as localizing prey or finding potential mates. In non-migrating bat species, playback studies showed that listening to vocalizations of other bats, both con-and heterospecifics, may help a recipient bat to find foraging patches and mating sites. However, we are still unaware of the degree to which migrating bats depend on con-or heterospecific vocalizations for identifying potential feeding or mating opportunities during nightly transit flights. Here, we investigated the vocal responses of Nathusius’ pipistrelle bats, Pipistrellus nathusii, to simulated feeding and courtship aggregations at a coastal migration corridor. We presented migrating bats either feeding buzzes or courtship calls of their own or a heterospecific migratory species, the common noctule, Nyctalus noctula. We expected that during migratory transit flights, simulated feeding opportunities would be particularly attractive to bats, as well as simulated mating opportunities which may indicate suitable roosts for a stopover. However, we found that when compared to the natural silence of both pre-and post-playback phases, bats called indifferently during the playback of conspecific feeding sounds, whereas P. nathusii echolocation call activity increased during simulated feeding of N. noctula. In contrast, the call activity of P. nathusii decreased during the playback of conspecific courtship calls, while no response could be detected when heterospecific call types were broadcasted. Our results suggest that while on migratory transits, P. nathusii circumnavigate conspecific mating aggregations, possibly to save time or to reduce the risks associated with social interactions where aggression due to territoriality might be expected. This avoidance behavior could be a result of optimization strategies by P. nathusii when performing long-distance migratory flights, and it could also explain the lack of a response to simulated conspecific feeding. However, the observed increase of activity in response to simulated feeding of N. noctula, suggests that P. nathusii individuals may be eavesdropping on other aerial hawking insectivorous species during migration, especially if these occupy a slightly different foraging niche., Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe; 1306

Supplementary methods, figures and tables.

Digital broad-band seismic recordings from station HLG on the small island of Heligoland in the German Bight in the North Sea are available since 2001. Since July 2017, an additional local network of six broad-band seismometers is operational on Heligoland with a focus on investigations of local microseism in the North Sea.In this study, we combine information gathered by passive seismic registration and gravity measurements from a superconducting gravimeter on Heligoland. We utilize 20 years of passive seismic data for long period spectral investigations spanning periods of tens of seconds up to several years. In the period band between 70 to 100 s, H/V ratios reveal strong noise on the horizontal components occurring contemporaneously with strong storms. In addition, distinct peaks in the spectral data are observed at periods of 6, 12 and 24 hours, which can be related to ocean tides and atmospheric pressure variations that are affecting the amplitude of local microseism. We compare the spectral seismic data with three years of gravity spectra from a collocated superconducting gravimeter. They are highly comparable with the seismic spectra and show distinct differences between local tides in the North Sea and solid Earth tides. At even longer periods up to several years, the spectral seismic data reveal a strong signal at one year, accompanied by peaks at 0.5, 2, 3 and 8 years. These variations seem to affect mostly the secondary microseism of the Northern Atlantic recorded at station HLG., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

An iGrav superconducting gravimeter has been installed on the small offshore island of Helgoland in the North Sea approximately at sea level with the overall aim of high-accuracy determination of regional ocean tide loading (OTL) and non-tidal ocean loading (NTOL) signals. For validation, a second gravimeter (gPhoneX) has been setup to observe temporal gravity variations in parallel on the upper land of Helgoland. The first part of this study covers the determination of regional OTL parameters after elimination of the height-dependent gravity component by empirical transfer functions between the local sea level from a nearby tide gauge and local attraction effects. After reduction of all gravity recordings to sea level, the regional OTL parameters from both gravimeters agree at the level of a few 0.1 nm/s². The second part of this study shows the gravity residuals that are largely dominated by regional NTOL signals. Driven by strong westerly and easterly winds, the water level fluctuates between 1.15 m above mean high water and 1.50 m below mean low water, inducing gravity increases of up to 30 nm/s² and decreases of down to -40 nm/s², respectively, during the analysed time period. These high-accuracy gravity observations will be used as “ground truth” for the calibration and validation of ocean tide models and satellite gravimetry from GRACE Follow-On as well as corresponding de-aliasing products. Finally, the SG network in Central Europe will strongly benefit from an improved knowledge of non-tidal ocean loading signals of the North Sea., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)