Max Planck Institute for Ornithology (Radolfzell)

Radolfzell, Germany

Max Planck Institute for Ornithology (Radolfzell)

Radolfzell, Germany
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Beekman M.,University of Sydney | Jordan L.A.,Max Planck Institute for Ornithology (Radolfzell)
Behavioral Ecology | Year: 2017

The field of animal personalities claims to fill a gap in our understanding of animal behavior, because it explicitly studies the adaptive significance of behavioral differences. This is a controversial claim given that the field of behavioral ecology firmly places the study of animal behavior in an evolutionary context. In fact, it is the evolutionary context that differentiates behavioral ecology from ethology and animal behavior, 2 fields that were already concerned with the study of behavior in nonhuman animals. So, if behavioral ecology already takes an evolutionary approach to variation in behavior, we ask what is personality research about exactly? This question is particularly pertinent now the focus of personality research shifts and the field moves away from being mainly descriptive to include quantitative frameworks. As a result, the field has come to borrow heavily from already established fields. In our view, this has resulted in "animal personality" studies becoming nothing more than a rebranding of existing fields of research - fields that are far more solidly grounded and hypothesis driven than the often vague and superficial focus on animal personalities. © The Author 2017. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.

Delhey K.,Max Planck Institute for Ornithology (Radolfzell)
Ecography | Year: 2017

Gloger's rule is usually interpreted as predicting darker coloured animals in warmer and more humid/vegetated regions. The relative importance of temperature and rainfall or vegetation is however unclear, and often only one variable is tested at a time, mainly through proxies. Here, I assess the predictions of Gloger's rule for interspecific achromatic plumage variation (dark to light variation) for an entire avifauna (551 species of Australian landbirds). I tested the effects of climatic variables (temperature and rainfall) and vegetation structure on plumage reflectance at species and assemblage level (100 × 100 km cells), controlling for phylogenetic relatedness and spatial autocorrelation. To assess the robustness of these results I compared observed results with those of a null distribution of effects obtained from repeatedly simulating random plumage reflectance evolution on the phylogeny. At both the species and assemblage level, darker coloured birds were found in wetter and colder regions and in more densely vegetated habitats. Simulations confirm results at the species level and the effect of temperature at the assemblage level, but rainfall and vegetation effects at the assemblage level fall within the distribution of simulated effects and should be interpreted with care. Interspecific colour variation in Australian birds supports Gloger's rule for rainfall/vegetation, but shows the opposite pattern for temperature. Darker colours in wet and vegetated environments are consistent with the role of melanin pigmentation in preventing feather degradation by bacteria, but also with background-matching for camouflage. Darker plumage might be beneficial in colder regions or detrimental in warmer regions if it affects thermoregulation, a selective force often only assumed to be of importance for ectotherms. The data highlight the need to test the generality of biogeographic rules across levels and at broad scale. Experimental work is needed to confirm the mechanisms linking plumage achromatic variation to climate. © 2017 Nordic Society Oikos.

Pulido F.,Max Planck Institute for Ornithology (Radolfzell) | Pulido F.,Netherlands Institute of Ecology | Pulido F.,Complutense University of Madrid | Berthold P.,Max Planck Institute for Ornithology (Radolfzell)
Proceedings of the National Academy of Sciences of the United States of America | Year: 2010

Global warming is impacting biodiversity by altering the distribution, abundance, and phenology of a wide range of animal and plant species. One of the best documented responses to recent climate change is alterations in the migratory behavior of birds, but the mechanisms underlying these phenotypic adjustments are largely unknown. This knowledge is still crucial to predict whether populations of migratory birds will adapt to a rapid increase in temperature. We monitored migratory behavior in a population of blackcaps (Sylvia atricapilla) to test for evolutionary responses to recent climate change. Using a common garden experiment in time and captive breeding we demonstrated a genetic reduction in migratory activity and evolutionary change in phenotypic plasticity of migration onset. An artificial selection experiment further revealed that residency will rapidly evolve in completely migratory bird populations if selection for shorter migration distance persists. Our findings suggest that current alterations of the environment are favoring birds wintering closer to the breeding grounds and that populations of migratory birds have strongly responded to these changes in selection. The reduction of migratory activity is probably an important evolutionary process in the adaptation of migratory birds to climate change, because it reduces migration costs and facilitates the rapid adjustment to the shifts in the timing of food availability during reproduction.

Gardner J.L.,Australian National University | Peters A.,Max Planck Institute for Ornithology (Radolfzell) | Peters A.,Monash University | Kearney M.R.,University of Melbourne | And 2 more authors.
Trends in Ecology and Evolution | Year: 2011

A recently documented correlate of anthropogenic climate change involves reductions in body size, the nature and scale of the pattern leading to suggestions of a third universal response to climate warming. Because body size affects thermoregulation and energetics, changing body size has implications for resilience in the face of climate change. A review of recent studies shows heterogeneity in the magnitude and direction of size responses, exposing a need for large-scale phylogenetically controlled comparative analyses of temporal size change. Integrative analyses of museum data combined with new theoretical models of size-dependent thermoregulatory and metabolic responses will increase both understanding of the underlying mechanisms and physiological consequences of size shifts and, therefore, the ability to predict the sensitivities of species to climate change. © 2011 Elsevier Ltd.

Helm B.,Max Planck Institute for Ornithology (Radolfzell) | Visser M.E.,Netherlands Institute of Ecology
Proceedings of the Royal Society B: Biological Sciences | Year: 2010

Timing is essential, but circadian clocks, which play a crucial role in timekeeping, are almost unaddressed in evolutionary ecology. A key property of circadian clocks is their free-running period length (t), i.e. the time taken for a full cycle under constant conditions. Under laboratory conditions, concordance of twith the ambient light-dark cycle confers major fitness benefits, but little is known about period length and its implications in natural populations. We therefore studied natural variation of circadian traits in a songbird, the great tit (Parus major), by recording locomotor activity of 98 hand-raised, wild-derived individuals. We found, unexpectedly, that the free-running period of this diurnal species was significantly shorter than 24 h in constant dim light. We furthermore demonstrate, to our knowledge for the first time in a wild vertebrate, ample genetic variation and high heritability (h 2 = 0.86+0.24), implying that period length is potentially malleable by micro-evolutionary change. The observed, short period length may be a consequence of sexual selection, as offspring from extra-pair matings had significantly shorter free-running periods than their half-siblings from within-pair matings. These findings position circadian clocks in the 'real world' and underscore the value of using chronobiological approaches in evolutionary ecology. Evolutionary ecologists study variation and its fitness consequences, but often have difficulties relating behavioural variation to physiological mechanisms. The findings presented here open the possibility that properties of internal, circadian clocks affect performance in traits that are relevant to fitness and sexual selection. © 2010 The Royal Society.

Riehl C.,Princeton University | Riehl C.,Max Planck Institute for Ornithology (Radolfzell)
Proceedings of the Royal Society B: Biological Sciences | Year: 2011

The greater ani (Crotophaga major), a Neotropical cuckoo, exhibits an unusual breeding system in which several socially monogamous pairs lay eggs in a single nest and contribute care to the communal clutch. Cooperative nesting is costly-females compete for reproduction by ejecting each other's eggs-but the potential direct or indirect fitness benefits that might accrue to group members have not been identified. In this study, I used molecular genotyping to quantify patterns of genetic relatedness and individual reproductive success within social groups in a single colour-banded population. Microsatellite analysis of 122 individuals in 49 groups revealed that group members are not genetic relatives. Group size was strongly correlated with individual reproductive success: solitary pairs were extremely rare and never successful, and nests attended by two pairs were significantly more likely to be depredated than were nests attended by three pairs. Egg loss, a consequence of reproductive competition, was greater in large groups and disproportionately affected females that initiated laying. However, early-laying females compensated for egg losses by laying larger clutches, and female group members switched positions in the laying order across nesting attempts. The greater ani, therefore, appears to be one of the few species in which cooperative breeding among unrelated individuals is favoured by direct, shared benefits that outweigh the substantial costs of reproductive competition. © 2010 The Royal Society.

Holland R.A.,Max Planck Institute for Ornithology (Radolfzell)
Journal of the Royal Society Interface | Year: 2010

In migratory passerine birds, strong magnetic pulses are thought to be diagnostic of the remagnetization of iron minerals in a putative sensory system contained in the beak. Previous evidence suggests that while such a magnetic pulse affects the orientation of migratory birds in orientation cages, no effect was present when pulse-treated birds were tested in natural migration. Here we show that two migrating passerine birds treated with a strong magnetic pulse, designed to alter the magnetic sense, migrated in a direction that differed significantly from that of controls when tested in natural conditions. The orientation of treated birds was different depending on the alignment of the pulse with respect to the magnetic field. These results can aid in advancing understanding of how the putative iron-mineral-based receptors found in birds' beaks may be used to detect and signal the intensity and/or direction of the Earth's magnetic field. © 2010 The Royal Society.

Dominoni D.,Max Planck Institute for Ornithology (Radolfzell)
Proceedings. Biological sciences / The Royal Society | Year: 2013

Artificial light at night is a rapidly increasing phenomenon and it is presumed to have global implications. Light at night has been associated with health problems in humans as a consequence of altered biological rhythms. Effects on wild animals have been less investigated, but light at night has often been assumed to affect seasonal cycles of urban dwellers. Using light loggers attached to free-living European blackbirds (Turdus merula), we first measured light intensity at night which forest and city birds are subjected to in the wild. Then we used these measurements to test for the effect of light at night on timing of reproductive physiology. Captive city and forest blackbirds were exposed to either dark nights or very low light intensities at night (0.3 lux). Birds exposed to light at night developed their reproductive system up to one month earlier, and also moulted earlier, than birds kept under dark nights. Furthermore, city birds responded differently than forest individuals to the light at night treatment, suggesting that urbanization can alter the physiological phenotype of songbirds. Our results emphasize the impact of human-induced lighting on the ecology of millions of animals living in cities and call for an understanding of the fitness consequences of light pollution.

Delhey K.,Max Planck Institute for Ornithology (Radolfzell)
Proceedings. Biological sciences / The Royal Society | Year: 2013

Colour signals are expected to match visual sensitivities of intended receivers. In birds, evolutionary shifts from violet-sensitive (V-type) to ultraviolet-sensitive (U-type) vision have been linked to increased prevalence of colours rich in shortwave reflectance (ultraviolet/blue), presumably due to better perception of such colours by U-type vision. Here we provide the first test of this widespread idea using fairy-wrens and allies (Family Maluridae) as a model, a family where shifts in visual sensitivities from V- to U-type eyes are associated with male nuptial plumage rich in ultraviolet/blue colours. Using psychophysical visual models, we compared the performance of both types of visual systems at two tasks: (i) detecting contrast between male plumage colours and natural backgrounds, and (ii) perceiving intraspecific chromatic variation in male plumage. While U-type outperforms V-type vision at both tasks, the crucial test here is whether U-type vision performs better at detecting and discriminating ultraviolet/blue colours when compared with other colours. This was true for detecting contrast between plumage colours and natural backgrounds (i), but not for discriminating intraspecific variability (ii). Our data indicate that selection to maximize conspicuousness to conspecifics may have led to the correlation between ultraviolet/blue colours and U-type vision in this clade of birds.

Dominoni D.M.,Max Planck Institute for Ornithology (Radolfzell)
Proceedings. Biological sciences / The Royal Society | Year: 2013

To keep pace with progressing urbanization organisms must cope with extensive habitat change. Anthropogenic light and noise have modified differences between day and night, and may thereby interfere with circadian clocks. Urbanized species, such as birds, are known to advance their activity to early morning and night hours. We hypothesized that such modified activity patterns are reflected by properties of the endogenous circadian clock. Using automatic radio-telemetry, we tested this idea by comparing activity patterns of free-living forest and city European blackbirds (Turdus merula). We then recaptured the same individuals and recorded their activity under constant conditions. City birds started their activity earlier and had faster but less robust circadian oscillation of locomotor activity than forest conspecifics. Circadian period length predicted start of activity in the field, and this relationship was mainly explained by fast-paced and early-rising city birds. Although based on only two populations, our findings point to links between city life, chronotype and circadian phenotype in songbirds, and potentially in other organisms that colonize urban habitats, and highlight that urban environments can significantly modify biologically important rhythms in wild organisms.

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