Structurally rich dry grasslands – Potential stepping stones for bats in open farmland

Agricultural intensification has caused decrease and fragmentation of European semi-natural dry grasslands. While a high biodiversity value of dry grasslands is acknowledged for plants and insects, locally and on landscape level, their relevance for mobile species, such as bats, is unknown. Here we investigate the use of dry grassland fragments by bats in an agriculturally intensified region in Germany and evaluate local and landscape factors influencing bat activity and assemblages. Specifically, we predicted that a combination of local dry grassland structural richness and landscape features as well as their interactions affect bat activity and foraging above dry grasslands. We also expected that these features influence compositions of local bat assemblages. We repeatedly sampled at 12 dry grassland plots with acoustic monitoring and assessed activity and foraging of bat species/sonotypes, which we grouped into guilds known for foraging in open land, at vegetation edges and in narrow spaces. We determined structural richness of the dry grassland plots in field and derived landscape features from digital landscape data. A relatively high proportion of bat species/sonotypes used dry grasslands regularly. The edge space foragers responded positively to higher local structural richness. Their dry grassland use increased when surrounding forests and woody features were less available, but they foraged more on dry grasslands closer to water bodies. Narrow space bat activity on dry grasslands decreased with less landscape connectivity. Open and narrow space foragers responded to local structural richness only in landscape context. For all bat guilds we found increased use of structurally richer dry grasslands when there was more open farmland in the surroundings. This was also the case for edge space foragers, when landscapes were more homogeneous. Lastly, with increasing structural richness, bat assemblages were more dominated by edge space foragers. We show the importance of European dry grassland fragments for the highly mobile group of bats under certain local structural and landscape compositional conditions. Our results underline the value of heterogeneous dry grassland fragments as potential stepping stones in intensively used farmland areas and contribute to evidence based decision making in dry grassland management and bat conservation

Methods for the automatic recording of bird calls and songs in field ornithology

Der gegenwärtige Kenntnisstand über automatisierte Methoden zur akustischen Erfassung von Rufen und Gesängen von Vögeln wird dargelegt. Die Grundlage für eine automatisierte Erfassung bilden Langzeitaufzeichnungen. Es wird der Frage nachgegangen, inwiefern Tonaufzeichnungen für eine qualitative und auch quantitative Analyse von Vogelbeständen geeignet sind. Spezielles Augenmerk wird autonomen Aufzeichnungsmethoden und der Auswertung von Langzeitaufzeichnungen unter Nutzung von Algorithmen der akustischen Mustererkennung gewidmet. Sinnvolle Einsatzszenarien für automatisierte Methoden im Rahmen avifaunistischer Feldforschung sind die Erfassung des nächtlichen Vogelzuges, die Erfassung nachtaktiver Brutvogelarten und die Datenerhebung in Kernzonen von Schutzgebieten.This review presents our current knowledge on automated methods for acoustic recording of calls and songs of birds. Acoustic long-term recordings can serve as a basis for an automated bird census. We stress the question of whether sound recordings are suitable for qualitative and quantitative analysis of bird populations. Special attention is devoted to autonomous recording methods and the evaluation of long-term recordings by use of acoustic pattern recognition algorithms. Realistic scenarios for the use of automated methods in field ornithology we see in the investigation of nocturnal bird migration, the census of nocturnal bird species, and data collection in core areas of nature reserves

Structurally rich dry grasslands – Potential stepping stones for bats in open farmland

Agricultural intensification has caused decrease and fragmentation of European semi-natural dry grasslands. While a high biodiversity value of dry grasslands is acknowledged for plants and insects, locally and on landscape level, their relevance for mobile species, such as bats, is unknown. Here we investigate the use of dry grassland fragments by bats in an agriculturally intensified region in Germany and evaluate local and landscape factors influencing bat activity and assemblages. Specifically, we predicted that a combination of local dry grassland structural richness and landscape features as well as their interactions affect bat activity and foraging above dry grasslands. We also expected that these features influence compositions of local bat assemblages. We repeatedly sampled at 12 dry grassland plots with acoustic monitoring and assessed activity and foraging of bat species/sonotypes, which we grouped into guilds known for foraging in open land, at vegetation edges and in narrow spaces. We determined structural richness of the dry grassland plots in field and derived landscape features from digital landscape data. A relatively high proportion of bat species/sonotypes used dry grasslands regularly. The edge space foragers responded positively to higher local structural richness. Their dry grassland use increased when surrounding forests and woody features were less available, but they foraged more on dry grasslands closer to water bodies. Narrow space bat activity on dry grasslands decreased with less landscape connectivity. Open and narrow space foragers responded to local structural richness only in landscape context. For all bat guilds we found increased use of structurally richer dry grasslands when there was more open farmland in the surroundings. This was also the case for edge space foragers, when landscapes were more homogeneous. Lastly, with increasing structural richness, bat assemblages were more dominated by edge space foragers. We show the importance of European dry grassland fragments for the highly mobile group of bats under certain local structural and landscape compositional conditions. Our results underline the value of heterogeneous dry grassland fragments as potential stepping stones in intensively used farmland areas and contribute to evidence based decision making in dry grassland management and bat conservation

The Song of the Sirens

In Homer’s account of the adventurous journey of Odysseus, the song of the sirens was so appealing and tempting that it lured sailors to their deaths. Warned by the goddess Kirke, Odysseus overcame the trap by plugging his crew’s ears with wax. An archaeo-acoustical research expedition undertaken by members of Humboldt University Berlin made sound propagation experiments at the supposedly historical scene at the Galli Islands where it’s said that the sirens originally sung. At the site we broadcasted both synthetic signals and natural voices via loudspeakers in the direction Odysseus most probably should have approached the Siren’s island. Subjective listening as well as objective acoustic analysis of the recorded signals revealed evidence for a combination of site-specific acoustic effects, which may explain the nature and origin of the song of the sirens in Homer. The local arrangement of the three islands deforms the acoustic signals by amplification and by changes in timbre. Two female singers from the Berlin State Opera were asked to sing differently pitched musical intervals to be tested in the Li Galli environment. The experiment evinced that the first overtones (octave, fifth, and fourths) would be merged by the echo of the rocks; yet when singing pure thirds and less consonant intervals, which yield higher orders in the overtone series, the voices appear recognisable as being two. As a result, and particularly because Homer stresses the number of exactly two sirens several times, the evidence of our research supports the musicological theory for a rather early existence of enharmonic tunings and most prominently a two-part polyphonic singing of Greek songs. Given that the rocky formation of the Galli Islands most likely didn’t change during the geological tick of just 2,700 years, we conclude that there has been a real acoustic basis for the myth reported by Homer and that a “song of the Sirens”, most probably based on natural voices, was transformed by the particular acoustic conditions of the landscape in such a way that signals were amplified and sent out in one concrete direction. Based on these results, we continue to discuss further leading acoustic theories that offer new insights into the mythology and which were essential to motivate our expedition in the first place. After all, the question remains open what kind of beings the first emitters of the song might have been

Vocalizations in juvenile anurans: common spadefoot toads (Pelobates fuscus) regularly emit calls before sexual maturity

Acoustic communication is prominent in adult anuran amphibians, in reproductive, territorial and defensive contexts. In contrast, reports on vocalizations of juvenile anurans are rare and anecdotal, and their function unstudied. We here provide conclusive evidence for vocalizations in juvenile spadefoot toads (Pelobates fuscus) in very early terrestrial stages. While the aquatic tadpoles did not emit sounds, first vocalizations of metamorphs were heard as early as in stages 42-43, and calls were regularly emitted from stage 44 on, often from specimens still bearing extensive tail stubs. Three main types of calls could be distinguished, of which one consists of a series of short notes, one of a typically single longer and pulsed note, and one of a single tonal note. In experimental setups, the number of calls per froglet increased with density of individuals and after feeding, while on the contrary calls were not elicited by playback. The function of these juvenile calls remains un-clarified, but they might reflect a general arousal in the context of feeding. Further evidence is necessary to test whether such feeding calls could confer a signal to conspecifics and thus might represent intraspecific acoustic communication in these immature terrestrial amphibians