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

Malaria parasites, immune challenge, MHC variability, and predator avoidance in a passerine bird

Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved. Several hypotheses predict a relationship between parasite burden and risk-taking behavior, but the underlying causal mechanisms are poorly understood due to the scarcity of experimental studies and the neglected focus on immune defense. Here, in 3 sets of field studies on the collared flycatcher, Ficedula albicollis, we investigated how among-male variation in flight initiation distance (FID, the distance at which an individual flee a potential predator) is linked to among-male variation in health status. First, we correlatively assessed the relationship between FID and the prevalence of haemosporidian blood parasites. We found no difference in risk-taking behavior between parasitized and nonparasitized individuals rejecting a hypothesis that predicts that malaria infection status affects the costs of predator avoidance. Second, we performed an immune challenge experiment, in which randomly chosen birds were injected with a novel antigen (sheep red blood cell) and their change in FID was compared with birds that received a placebo treatment. This experiment revealed no evidence for the immunological treatment affecting risk-taking behavior, thus we failed to obtain support for the hypothesis that posits that immediate health status mediates decisions about when to flee a predator. Finally, we detected a negative relationship between the number of alleles of the major histocompatibility complex and FID. This result, in concordance with the above negative results, supports the >avoidance> hypothesis that states that only individuals with efficient immune defense machinery are able to bear the costs of risk-taking that can emerge through the increased infection rates of risk-taker individuals.Peer Reviewe