Institute of Avian Research Vogelwarte Helgoland

Wilhelmshaven, Germany

Institute of Avian Research Vogelwarte Helgoland

Wilhelmshaven, Germany
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Schmaljohann H.,Institute of Avian Research Vogelwarte Helgoland | Both C.,University of Groningen
Nature Climate Change | Year: 2017

Predicting the range of variation over which organisms can adjust to environmental change is a major challenge in ecology. This is exemplified in migratory birds which experience changes in different habitats throughout the annual cycle. Earlier studies showed European population trends declining strongest in migrant species with least adjustment in spring arrival time. Thus, the increasing mismatches with other trophic levels in seasonal breeding areas probably contribute to their large-scale decline. Here we quantify the potential range of adjusting spring arrival dates through modifying migration speeds by reviewing 49 tracking studies. Among-individual variation in migration speed was mainly determined by the relatively short stop-over duration. Assuming this population response reflects individual phenotypic plasticity, we calculated the potential for phenotypic plasticity to speed-up migration by reducing stop-over duration. Even a 50% reduction would lead to a mere two-day advance in arrival, considering adjustments on the final 2,000 km of the spring journey. Hence, in contrast to previous studies, flexibility in the major determinant of migration duration seems insufficient to adjust to ongoing climate change, and is unlikely to explain some of the observed arrival advancements in long-distance migrants. © 2017 Macmillan Publishers Limited.


Bauch C.,Institute of Avian Research Vogelwarte Helgoland | Becker P.H.,Institute of Avian Research Vogelwarte Helgoland | Verhulst S.,University of Groningen
Molecular Ecology | Year: 2014

Telomeres, DNA-protein structures at chromosome ends, shorten with age, and telomere length has been linked to age-related diseases and survival. In vitro studies revealed that the shortest telomeres trigger cell senescence, but whether the shortest telomeres are also the best biomarker of ageing is not known. We measured telomeres in erythrocytes of wild common terns Sterna hirundo using terminal restriction fragment analysis. This yields a distribution of telomere lengths for each sample, and we investigated how different telomere subpopulations (percentiles) varied in their relation to age and fitness proxies. Longer telomeres within a genome lost more base pairs with age and were better predictors of survival than shorter telomeres. Likewise, fitness proxies such as arrival date at the breeding grounds and reproductive success were best predicted by telomere length at the higher percentiles. Our finding that longer telomeres within a genome predict fitness components better than the shorter telomeres indicates that they are a more informative ageing biomarker. This finding contrasts with the fact that cell senescence is triggered by the shortest telomeres. We suggest that this paradox arises, because longer telomeres lose more base pairs per unit time and thus better reflect the various forms of stress that accelerate telomere shortening, and that telomeres primarily function as biomarker because their shortening reflects cumulative effects of various stressors rather than reflecting telomere-induced cell senescence. © 2013 John Wiley & Sons Ltd.


Bauch C.,Institute of Avian Research Vogelwarte Helgoland | Becker P.H.,Institute of Avian Research Vogelwarte Helgoland | Verhulst S.,University of Groningen
Proceedings of the Royal Society B: Biological Sciences | Year: 2013

Telomere length is associated with cellular senescence, lifestyle and ageing. Short telomeres indicate poor health in humans and reduced life expectancy in several bird species, but little is known about telomeres in relation to phenotypic quality in wild animals. We investigated telomere lengths in erythrocytes of known-age common terns (Sterna hirundo), a migratory seabird, in relation to arrival date and reproductive performance. Cross-sectional data revealed that, independent of age, individuals with short telomeres performed better: they arrived and reproduced earlier in the season and had more chicks in the nest. The latter effect was stronger the older the brood and stronger in males, which do most of the chick provisioning. Longitudinal data confirmed this pattern: compared with birds that lost their brood, birds that raised chicks beyond the 10th nestling day experienced higher telomere attrition from one year to the next. However, more detailed analysis revealed that the least and most successful individuals lost the fewest base pairs compared with birds with intermediate success. Our results suggest that reproductive success is achieved at the expense of telomeres, but that individual heterogeneity in susceptibility to such detrimental effects is important, as indicated by low telomere loss in the most successful birds. © 2012 The Author(s) Published by the Royal Society. All rights reserved.


Bauch C.,Institute of Avian Research Vogelwarte Helgoland
Proceedings. Biological sciences / The Royal Society | Year: 2013

Telomere length is associated with cellular senescence, lifestyle and ageing. Short telomeres indicate poor health in humans and reduced life expectancy in several bird species, but little is known about telomeres in relation to phenotypic quality in wild animals. We investigated telomere lengths in erythrocytes of known-age common terns (Sterna hirundo), a migratory seabird, in relation to arrival date and reproductive performance. Cross-sectional data revealed that, independent of age, individuals with short telomeres performed better: they arrived and reproduced earlier in the season and had more chicks in the nest. The latter effect was stronger the older the brood and stronger in males, which do most of the chick provisioning. Longitudinal data confirmed this pattern: compared with birds that lost their brood, birds that raised chicks beyond the 10th nestling day experienced higher telomere attrition from one year to the next. However, more detailed analysis revealed that the least and most successful individuals lost the fewest base pairs compared with birds with intermediate success. Our results suggest that reproductive success is achieved at the expense of telomeres, but that individual heterogeneity in susceptibility to such detrimental effects is important, as indicated by low telomere loss in the most successful birds.


Maggini I.,Institute of Avian Research Vogelwarte Helgoland | Bairlein F.,Institute of Avian Research Vogelwarte Helgoland
PLoS ONE | Year: 2012

In migrating animals protandry is the phenomenon whereby males of a species arrive at the breeding grounds earlier than females. In the present study we investigated the proximate causes of protandry in a migratory songbird, the northern wheatear Oenanthe oenanthe. Previous experiments with caged birds revealed that males and females show differentiated photoperiod-induced migratory habits. However, it remained open whether protandry would still occur without photoperiodic cues. In this study we kept captive first-year birds under constant photoperiod and environmental conditions in a "common garden" experiment. Male northern wheatears started their spring migratory activity earlier than females, even in the absence of environmental cues. This indicates that protandry in the northern wheatear has an endogenous basis with an innate earlier spring departure of males than females. © 2012 Maggini, Bairlein.


Szostek K.L.,Institute of Avian Research Vogelwarte Helgoland | Schaub M.,Swiss Ornithological Institute | Becker P.H.,Institute of Avian Research Vogelwarte Helgoland
Journal of Animal Ecology | Year: 2014

Immigration is a major demographic factor shaping population dynamics. However, due to methodological difficulties, the extent of immigration and factors affecting immigration are insufficiently studied. This is also true for seabird colonies. We estimated annual immigration based on a long-term study of a colony of common terns Sterna hirundo marked with transponders, using a Bayesian integrated population model that links colony size and productivity with individual life histories. Strong annual fluctuations in the number of immigrants were found. To identify whether colony-specific covariates influenced immigration, we related the number of immigrants to various proxy variables for breeding site quality, specifically colony size, productivity, number of local subadults and local recruits. Numbers of local recruits and local subadults showed strong positive correlations with number of immigrants. We found that variation in immigration rate had strongly contributed to variation in colony growth rate, more so than variation in local recruitment or adult survival. Collectively, results suggest that immigration strongly affects colony growth rate, that the driving force behind immigration is natal dispersal and that immigrants were attracted by local recruits. © 2014 British Ecological Society.


Zhang H.,Institute of Avian Research Vogelwarte Helgoland | Rebke M.,Avitec Research GbR | Becker P.H.,Institute of Avian Research Vogelwarte Helgoland | Bouwhuis S.,Institute of Avian Research Vogelwarte Helgoland
Journal of Animal Ecology | Year: 2015

Summary: Reproductive value is an integrated measure of survival and reproduction fundamental to understanding life-history evolution and population dynamics, but little is known about intraspecific variation in reproductive value and factors explaining such variation, if any. By applying generalized additive mixed models to longitudinal individual-based data of the common tern Sterna hirundo, we estimated age-specific annual survival probability, breeding probability and reproductive performance, based on which we calculated age-specific reproductive values. We investigated effects of sex and recruitment age (RA) on each trait. We found age effects on all traits, with survival and breeding probability declining with age, while reproductive performance first improved with age before levelling off. We only found a very small, marginally significant, sex effect on survival probability, but evidence for decreasing age-specific breeding probability and reproductive performance with RA. As a result, males had slightly lower age-specific reproductive values than females, while birds of both sexes that recruited at the earliest ages of 2 and 3 years (i.e. 54% of the tern population) had somewhat higher fitness prospects than birds recruiting at later ages. While the RA effects on breeding probability and reproductive performance were statistically significant, these effects were not large enough to translate to significant effects on reproductive value. Age-specific reproductive values provided evidence for senescence, which came with fitness costs in a range of 17-21% for the sex-RA groups. Our study suggests that intraspecific variation in reproductive value may exist, but that, in the common tern, the differences are small. © 2014 British Ecological Society.


Randler C.,University of Education, Heidelberg | Forschler M.I.,Institute of Avian Research Vogelwarte Helgoland
Animal Behaviour | Year: 2011

Passerine mobbing calls are, in part, addressed to conspecific and heterospecific prey individuals, and may encourage them to join a flock mobbing a predator. We examined whether conspecific and heterospecific individuals differ in their response to natural and manipulated contact and mobbing calls. We assumed that conspecifics would be more sensitive to slight variation in call elements and manipulations, whereas heterospecifics most likely cannot distinguish subtle differences. We used chaffinch, Fringilla coelebs, contact and mobbing calls, which differ only slightly in structure (start and maximum frequency and frequency bandwidth). Despite these subtle differences in call parameters, mobbing calls of chaffinches could be transformed into artificial contact calls by using fewer elements/min, and vice versa. Contact calls could be transformed into mobbing calls by reducing the pauses between the single elements. The results show that intense calling attracted more conspecific and heterospecific prey individuals than less intense playbacks of the calls made of the same elements. Responses to natural calls compared to manipulated calls were similar in minimum distance to the speaker in conspecifics and heterospecifics, in the number of conspecific and heterospecific individuals alerted and in the number of heterospecific species attracted. The frequency of calls per time unit was the most significant factor affecting whether other birds interpreted the vocalization as a mobbing or a contact call. In conspecifics, the effect sizes of the response were smaller, suggesting that conspecifics perceive the manipulation as conflicting information. © 2011 The Association for the Study of Animal Behaviour.


Huppop O.,Institute of Avian Research Vogelwarte Helgoland | Hilgerloh G.,Institute of Avian Research Vogelwarte Helgoland
Journal of Avian Biology | Year: 2012

Many bird species call during migration, but call rates not necessarily reflect migration intensity. They rather seem to increase under deteriorating flight conditions. Often, nocturnal mass collisions at illuminated structures coincide with such conditions and are accompanied with high call rates of migrants. Thus, call rates could act as an indicator for situations with high collision risk for birds namely at offshore sites with hardly any alternatives for landing. In the face of increasing numbers of offshore wind farms knowledge about the environmental conditions in which maximum call rates occur, is needed for mitigation measures. In this first long-term study at an offshore site in the southern North Sea we investigated the effect of weather on the frequency of flight calls of three thrush-species at an illuminated platform. Flight calls were registered automatically during three autumn migration seasons. Besides generally higher call rates from 5 to 2 h before until 6 h after midnight, call rates increased with tailwinds, a change of the tailwind component during the first part of the night, offshore crosswinds and very high humidity. A monitoring programme is suggested that could help to reduce mass mortalities at illuminated structures. © 2012 The Authors. Journal of Avian Biology © 2012 Nordic Society Oikos.


Schmaljohann H.,Institute of Avian Research Vogelwarte Helgoland | Fox J.W.,Migrate Technology Ltd | Bairlein F.,Institute of Avian Research Vogelwarte Helgoland
Animal Behaviour | Year: 2012

Migrants' responses to varying meteorological and magnetic conditions and their consequent costs in terms of energy and time are crucial for the understanding of the spatial principles guiding migration. Until now, studies of birds' phenotypic responses to environmental conditions and estimated costs of migration in terms of energy and time have focused on single sites and have rarely followed individuals along entire migration routes. We used individual-based light level geolocators to track birds' daily phenotypic responses to the environmental conditions experienced along a 30 000. km migration between Alaska and Africa. In autumn, departures of northern wheatears, Oenanthe oenanthe, were highly dependent on low temperatures and light winds but there was no such apparent dependence in spring. Migration was 1.4-times faster in spring than in autumn. There was an unexpected shift in the ratio of migration:stopover time towards less stopover time in spring, reducing spring's total energy costs for migration with respect to distance covered by nearly 50% in comparison to autumn. Despite strong changes in declination during migration, offering near-experimental conditions, birds did not navigate exclusively along any major compass course. In contrast to expectations, these high-Arctic migrants did not follow great circle routes; their hypothetical energetic benefit (ca. 20% for flying) might be insufficient and conditions for orientation too unfavourable to favour its evolution. © 2012 The Association for the Study of Animal Behaviour.

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