The relationship between syllable repertoire similarity and pairing success in a passerine bird species with complex song

Repertoire size, i.e. the number of unique song elements that an individual possesses, is thought to be an important target of female preference. However, the use of repertoire size reflects how researchers work with complex songs; while it does not necessary describe biological functions, as listeners of song may also rely on song composition. Specific syllables may have coherent consequences for mate attraction because they are costly to produce, mediate syllable sharing or indicate the dialect of origin. We tested for the relationship between song composition and pairing success in the collared flycatcher (Ficedula albicollis). We applied a tree-clustering method to hierarchically classify males based on the degree of repertoire overlap, and then used a phylogenetic approach to assess the degree by which pairing speed matches the hierarchically structured song data. We found that males using similar syllables also find a breeding partner at a similar speed. Partitioning the variance components of pairing speed, we detected that the consequences of particular syllables for mating are repeatable across males. When assessing the role of repertoire similarity in mediating direct syllable sharing, we derived a positive relationship between the physical distance between pairs of males and their repertoire overlap implying that neighboring males avoid copying each other's song. Finally, we were unable to demonstrate that syllables related to higher mating success are more common in the population, which would support mechanisms based on female preference for local songs. Our results imply that individual-specific song organization may be relevant for sexual selection. © 2011 Elsevier Ltd.Peer Reviewe

A test on within-individual changes in risk-taking behaviour due to experience to predation in the Collared Flycatcher (Ficedula albicollis)

Different experiences from the past may have influence on individual¿s behaviour through feedback mechanisms that can weaken or preserve the within-individual consistency of behavioural traits. Here, we aimed to find evidence for such feedback mechanisms that may operate on risk-taking behaviour via the effect of former experience to potential predation events in male Collared Flycatchers (Ficedula albicollis). We predicted that risk-taking of males would decrease after experiencing a predator¿s attack in previous breeding seasons (negative feedback). We assessed risk-taking by flight initiation distance (FID) that is the distance at which an individual flees from an approaching predator, which was estimated for 234 individuals from different breeding seasons. Information on predation experience (i.e. occurrence of nest predation, the incidence of capture by human observers) was available from our long-term database on individual life histories. In a horizontal approach, we found no difference in FID when comparing males with former experience to predation with males naive to predators. A longitudinal approach relying on the repeated tests of the same individuals from different years yielded analogous results, we could not show a significant change in the risk-taking behaviour of the males as a consequence of experience to predation in past years. However, we found that individuals systematically took less risk over the years, which might be a consequence of acquiring general experience with agePeer Reviewe

Acoustic mirrors as sensory traps for bats

Sensory traps pose a considerable and often fatal risk for animals, leading them to misinterpret their environment. Bats predominantly rely on their echolocation system to forage, orientate, and navigate.We found that bats can mistake smooth, vertical surfaces as clear flight paths, repeatedly colliding with them, likely as a result of their acoustic mirror properties. The probability of collision is influenced by the number of echolocation calls and by the amount of time spent in front of the surface. The echolocation call analysis corroborates that bats perceive smooth, vertical surfaces as open flyways. Reporting on occurrences with different species in the wild, we argue that it is necessary to more closely monitor potentially dangerous locations with acoustic mirror properties (such as glass fronts) to assess the true frequency of fatalities around these sensory traps

Global warming alters sound transmission: Differential impact on the prey detection ability of echolocating bats

Climate change impacts the biogeography and phenology of plants and animals, yet the underlying mechanisms are little known. Here, we present a functional link between rising temperature and the prey detection ability of echolocating bats. The maximum distance for echo-based prey detection is physically determined by sound attenuation. Attenuation is more pronounced for high-frequency sound, such as echolocation, and is a nonlinear function of both call frequency and ambient temperature. Hence, the prey detection ability, and thus possibly the foraging efficiency, of echolocating bats and susceptible to rising temperatures through climate change. Using present-day climate data and projected temperature rises, we modelled this effect for the entire range of bat call frequencies and climate zones around the globe. We show that depending on call frequency, the prey detection volume of bats will either decrease or increase: species calling above a crossover frequency will lose and species emitting lower frequencies will gain prey detection volume, with crossover frequency and magnitude depending on the local climatic conditions. Within local species assemblages, this may cause a change in community composition. Global warming can thus directly affect the prey detection ability of individual bats and indirectly their interspecific interactions with competitors and prey