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Hahn S.,Swiss Ornithological Institute | Amrhein V.,University of Basel | Amrhein V.,Research Station Petite Camargue Alsacienne | Zehtindijev P.,Bulgarian Academy of Science | Liechti F.,Swiss Ornithological Institute
Oecologia | Year: 2013

Whether migratory animals use similar resources during continental-scale movements that characterize their annual cycles is highly relevant to both individual performances and population dynamics. Direct knowledge of the locations and resources used by migrants during non-breeding is generally scarce. Our goal was to estimate migratory connectivity of a small Palaearctic long-distance migrant, the common nightingale Luscinia megarhynchos, and to compare resources used in non-breeding areas with resources used at the breeding grounds. We tracked individuals of three geographically separated populations and characterised their stable isotope niches during breeding and non-breeding over 2 years. Individuals spent the non-breeding period in population-specific clusters from west to central Africa, indicating strong migratory connectivity at the population level. Irrespective of origin, their isotopic niches were surprisingly similar within a particular period, although sites of residence were distant. However, niche characteristics differed markedly between breeding and non-breeding periods, indicating a consistent seasonal isotopic niche shift in the sampled populations. Although nightingales of distinct breeding populations migrated to different non-breeding areas, they chose similar foraging conditions within specific periods. However, nightingales clearly changed resource use between breeding and non-breeding periods, indicating adaptations to changes in food availability. © 2013 Springer-Verlag Berlin Heidelberg. Source


Sprau P.,Netherlands Institute of Ecology | Roth T.,Research Station Petite Camargue Alsacienne | Roth T.,University of Basel | Amrhein V.,Research Station Petite Camargue Alsacienne | And 3 more authors.
Animal Behaviour | Year: 2012

In communication networks, territorial neighbours often regulate social relations using long-range signals. However, such relations may be affected when unfamiliar third parties threaten the territorial integrity of the neighbourhood. We investigated responses of vocally interacting nightingales, . Luscinia megarhynchos, that were successively challenged by simulated rivals prospecting the neighbourhood. Using playback experiments, we tested whether territorial behaviour of males is affected differently dependent on whether their neighbours were challenged with aggressively or moderately singing rivals and whether information from the observed interaction is being used in subsequent encounters with the simulated prospector. Males sang more moderately the closer they were to a neighbour that was threatened by an aggressively singing rival. When challenged themselves, these males then discriminated between rivals depending on how they had previously interacted with their neighbour. Thus, males condition their vocal behaviour on their neighbour's situation and use information from neighbour-stranger interactions in future decision making. These findings reveal that in social networks, rivals' behaviour and distance to neighbours matter, emphasizing the importance of considering multiple individuals and their spatial relations when assessing the functions of territorial signalling. © 2012 The Association for the Study of Animal Behaviour. Source


Amrhein V.,Research Station Petite Camargue Alsacienne | Amrhein V.,University of Basel | Scaar B.,Research Station Petite Camargue Alsacienne | Baumann M.,Research Station Petite Camargue Alsacienne | And 4 more authors.
Methods in Ecology and Evolution | Year: 2012

1. It is increasingly acknowledged that skewed adult sex ratios (ASRs) may play an important role in ecology, evolution and conservation of animals. 2. In birds, published estimates on ASRsmostly rely onmist netting data. However, previous studies suggested that mist nets or other trap types provide biased estimates on sex ratios, with males being more susceptible to capture than females. 3. We used data from a Constant Effort Site ringing scheme to show how sex ratios that are corrected for sex- and year-specific capture probabilities can be directly estimated by applying capture-recapture analysis, for example, in a Bayesian framework. 4. When capture data were pooled from the 19 years of study, we found that in the blackbird (Turdus merula) and the blackcap (Sylvia atricapilla), the observed proportions of males were 57% and 55%, respectively. However, when the observed annual proportions of males were corrected for the sex-specific capture probabilities, the proportions of males did not clearly differ from50%in most study years, and thus, the apparent male-bias in the ASRs almost completely disappeared. 5. We propose that published estimates on ASRs in birds should be re-evaluated if based solely on observed sex ratios frommist netting studies. 6. We further propose that data from national bird ringing schemes and in particular from Constant Effort Site ringing programs can provide valuable information on ASRs, if analysed using capture-recapture models. We discuss important assumptions of those models; for example, movements that may differ between sexes should be taken into account, as well as the occurrence of transient individuals that do not hold breeding territories within a study site. © 2012 The Authors. Methods in Ecology and Evolution, © 2012 British Ecological Society. Source


Saggese K.,University of Basel | Saggese K.,University of Oslo | Korner-Nievergelt F.,Swiss Ornithological Institute | Korner-Nievergelt F.,Oikostat GmbH | And 3 more authors.
Animal Behaviour | Year: 2011

Supplementary feeding of wild birds during winter is one of the most popular wildlife management activities, and is likely to have profound influence on the behavioural ecology of a species. At garden bird feeders, birds are now often fed well into the breeding season. Providing food within an established songbird territory, however, is likely to influence the territorial behaviour of the resident male. We used song performance during the dawn chorus in early spring to study behavioural changes in food-supplemented great tits, Parus major. After 2 weeks of continuous food supply within their territory, supplemented males started dawn singing later than control males, and thus postponed their regular dawn chorus before sunrise. This effect was maintained 2 weeks after food supplementation had ended. However, we did not find an effect of long-term feeding on song output. Our results were largely unexpected because formal models and field studies on short-term food supplementation suggested an earlier start of dawn singing or a higher dawn song output. Because we did not observe great tits visiting the feeders before sunrise or food supplementation increasing the numbers of conspecific intruders, the reasons for the delay in the start of dawn singing remain unclear; possible explanations include the presence of predators at feeding stations and the quality of the supplementary food itself. Delaying dawn singing could potentially affect the reproductive success of supplemented males, for example if females base extrapair mating decisions on dawn song performance of their mates. © 2010 The Association for the Study of Animal Behaviour. Source


Roth T.,University of Basel | Roth T.,Research Station Petite Camargue Alsacienne | Buhler C.,Hintermann and Weber | Amrhein V.,University of Basel | Amrhein V.,Research Station Petite Camargue Alsacienne
American Naturalist | Year: 2016

Global change causes community composition to change considerably through time, with ever-new combinations of interacting species. To study the consequences of newly established species interactions, one available source of data could be observational surveys from biodiversity monitoring. However, approaches using observational data would need to account for niche differences between species and for imperfect detection of individuals. To estimate population sizes of interacting species, we extended N-mixture models that were developed to estimate true population sizes in single species. Simulations revealed that our model is able to disentangle direct effects of dominant on subordinate species from indirect effects of dominant species on detection probability of subordinate species. For illustration, we applied our model to data from a Swiss amphibian mon­itoring program and showed that sizes of expanding water frog populations were negatively related to population sizes of endangered yellow-bellied toads and common midwife toads and partly of natterjack toads. Unlike other studies that analyzed presence and absence ofspecies, our model suggests that the spread of water frogs in Central Europe is one of the reasons for the decline of endangered toad species. Thus, studying population impacts of dominant species on population sizes of endangered species using data from biodiversity monitoring programs should help to inform conservation policy and to decide whether competing species should be subject to population management. © 2016 by The University of Chicago. Source

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