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Osterholz-Scharmbeck, Germany

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. Source

Huppop K.,Institute For Vogelforschung Vogelwarte Helgoland | Dierschke J.,Institute For Vogelforschung Vogelwarte Helgoland | Hill R.,Avitec Research GbR | Huppop O.,Institute For Vogelforschung Vogelwarte Helgoland
Vogelwarte | Year: 2012

With regard to potential sites for the construction of offshore wind farms and to their possible threats for birds it is essential to enlarge the current knowledge on bird migration above the sea - especially during the night. Within a comprehensive study for the evaluation of offshore wind farms bird calls were registered automatically on a research platform in the south-eastern North Sea. The species identification of nocturnally migrating birds is almost exclusively possible only by means of their calls. Here, we present species-specific bird occurrence near an anthropogenic offshore structure in the total daily and yearly course on the basis of automatically registered calls. From 2004 to 2007, a total of 100 species was identified. Calls from 95,318 individuals (excluding the large gulls) were used for analyses. Three quarters were passerines (predominantly thrushes), furthermore mainly waders, terns and smaller gulls were detected. 79.4% of all individuals were registered during the night. High numbers of individuals, mostly of several species occurring together, were concentrated in only a few days/nights or even hours. Bird occurrence was much higher during autumn migration than during spring migration. A maximum of 5,236 birds of different species (corresponding to 392 Ind./h) was identified in the night from 28th to 29th October 2005. The migration periods of the short-/medium distance migrants were clearly distinguishable, otherwise not those of the long-distance passerine migrants, presumably due to their much minor ambition to call. In July mainly smaller gulls and terns, in August above all terns and waders (especially Redshank) and in winter some late smaller gulls and thrushes were registered. Generally, numbers increased continually with the beginning of the night and reached a maximum before sunrise. The fewest birds were detected in the late afternoon. Despite methodological constraints, the shown species-specific phenologies broadly match the migration times in the offshore area of the German Bight as recovered by trapping and/or by scheduled or coincidental visual observations of bird migration. Like these methods the acoustic recording cannot cover the whole occurrence of birds. Presumably, the number of birds is underestimated during fine and overestimated during adverse weather when birds reduce flight altitude. However, we assume that the birds registered acoustically on the platform reflect at least the low flying proportion of the calling species in the course of the year and in their daily variability. The opportunity to estimate numbers of low and thereby close to an anthropogenic obstruction flying birds using calls is - with regard to the evaluation of its collision risk and the introduction of mitigation and avoidance measures (site, short-term shutdown of the construction and optimization of illumination) - not exiguous. © DO-G, IfV, MPG 2012. Source

Frommolt K.-H.,Leibniz Institute For Evolutions Und Biodiversitatsforschung | Huppop O.,Institute For Vogelforschung Vogelwarte Helgoland | Bardeli R.,Fraunhofer Institute for Intelligent Analysis and Information Systems | Hill R.,Avitec Research GbR | And 3 more authors.
Vogelwarte | Year: 2012

This review presents our current knowledge on automated methods for acoustic recording of calls and songs of birds. Acoustic long-term recordings can serve as a basis for an automated bird census. We stress the question of whether sound recordings are suitable for qualitative and quantitative analysis of bird populations. Special attention is devoted to autonomous recording methods and the evaluation of long-term recordings by use of acoustic pattern recognition algorithms. Realistic scenarios for the use of automated methods in field ornithology we see in the investigation of nocturnal bird migration, the census of nocturnal bird species, and data collection in core areas of nature reserves. © DO-G, IfV, MPG 2012. Source

When addressing potential threats of offshore wind farms on migrating birds, avoidance behavior in response to wind farms is among those commonly mentioned, meaning that wind farms can act as barriers for migrants. Substantial - but otherwise sparsely - proof for this exits from Denmark and The Netherlands. However, monitoring potential threats in the German Bight failed in providing evidence of an avoidance response of migrating birds to offshore wind farms. Minor adaptations of the current method of investigation and analysis provided here, however, have led to substantiated results. In addition, these adaptations can easily be incorporated into current standard protocols of environmental impact assessment studies. Demonstrating this, we here present an example of avoidance behavior of gannets Sula bassana in particular to a wind farm and of birds in general. © DO-G, IfV, MPG 2013. Source

Aumuller R.,Avitec Research GbR | Boos K.,Avitec Research GbR | Freienstein S.,Avitec Research GbR | Hill K.,Avitec Research GbR | Hill R.,Avitec Research GbR
Vogelwarte | Year: 2011

The present work derives from currently undertaken ecological accompanying research at the offshore-windfarm 'alpha ventus', 45 km north of the North Sea island Borkum. Using remote detection techniques and visual observations, we present for the first time since initial data ascertainment in autumn 2003 a complete nights course of a bird mass-migration along with different weather parameters and a directly connected mass collision event at the research platform FINO1 in the night of the 1./2.11.2010. Increasing numbers of migrating birds from northeasterly directions were detected during the early evening of the 1.11.2010 and reached their peak of about 460 radar echoes/h between 19:00 and 20:00 h. Contemporaneous weather changes involving tailwinds changing to direct headwinds, increasing wind velocity and decreasing visibility led the birds to continuously descend to lower heights during the strongest migration period between 19:00 and 1:00 h. From 4:00 h onward, more than 50% of the migrating birds were detected in the lower flight heights of 200 m and below and suggest low-level flights to be a reaction towards sudden bad-weather appearances. Enhanced aggregation of birds in the effected area of FINO1 and operating wind turbines, respectively, increase their potential risk of collision by being drawn to the illuminated structures, and in fact, collisions were detected through video and infrared recordings at FINO1. With 88 birds found dead from the night of the 1/2.11.2010, this event holds fourth position of so far documented mass collision events at FINO1. Because the documentation of such (mass) collision events is generally obfuscated and often methodologically limited, the subsequent assessment of the threat for birds is still unknown. The presented event highlights the daunting quantitative dimensions of casualties with regard to future projected wind turbines. © DOG, IfV, MPG 2011. Source

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