Jorg Welcker

Jorg Welcker
Bio Consult SH

PhD

About

48
Publications
12,569
Reads
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1,666
Citations
Citations since 2017
10 Research Items
917 Citations
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2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150

Publications

Publications (48)
Article
Full-text available
Delayed maturity, low fecundity, and high adult survival are traits typical for species with a long-life expectancy. For such species, even a small change in adult survival can strongly affect the population dynamics and viability. We examined the effects of both regional and local climatic variability on adult survival of the little auk, a long-li...
Article
Full-text available
The number of offshore wind farms in Europe and elsewhere has substantially increased in recent years. This rapid development has raised concerns about potential impacts on marine wildlife, particularly on seabirds, as these can be negatively affected through collision and displacement. While collision risk has been the focus of a number of studies...
Article
Full-text available
Nocturnally migrating birds, particularly passerines, are known to be vulnerable to collision with manmade structures such as buildings, towers or offshore platforms, yet information with respect to wind farms is ambiguous. We recorded bird flight intensities using radar during autumn migration at four wind farms situated within a major migration f...
Article
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Global warming, combined with an increasing influence of Atlantic Waters in the European Arctic, are causing a so-called Atlantification of the Arctic. This phenomenon is affecting the plankton biomass and communities with potential consequences for the upper trophic levels. Using long-term data (2005-2020) from a high Arctic zooplanktivorous seabi...
Article
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Sharing the same wintering grounds by avian populations breeding in various areas may synchronize fluctuations in vital rates, which could increase the risk of extinction. Here, by combining multi-colony tracking with long-term capture-recapture data, we studied the winter distribution and annual survival of the most numerous Arctic seabird, the li...
Article
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Climate warming is rapidly altering marine ecosystems towards a more temperate state on the European side of the Arctic. However, this "Atlantification" has rarely been confirmed, as long-term datasets on Arctic marine organisms are scarce. We present a 19-year time series (1982-2016) of diet samples from black-legged kittiwakes as an indicator of...
Article
Early-life conditions can drive ageing patterns and life history strategies throughout the lifespan. Certain social, genetic, and nutritional developmental conditions are more likely to produce high-quality offspring: those with good likelihood of recruitment and productivity. Here we call such conditions "favored states" and explore their relation...
Article
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Sex allocation theory predicts that parents should bias offspring sex according to the costs and benefits associated with producing either sex in a given context. Accurately interpreting sex-ratio biases, therefore, requires a precise identification of these selective pressures. However, such information is generally lacking. This may partly explai...
Article
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1.Reproduction is energetically expensive, and daily energy expenditure (DEE) often peaks during the period of rearing young. The “potentiation” hypothesis predicts that high DEE needs to be sustained by a corresponding up-regulation of metabolic machinery, thus a concomitant increase of the resting metabolic rate (RMR) is expected. Alternatively,...
Data
Table S1. Parameter slope (β) estimates (±95% CI) for the top three models in step two. Φ = survival, NAO2 = the winter NAO (2-year time-lag), SST1 = summer SST (1-year time-lag), Intercept = Isfjorden, K = Kongsfjorden, B = Bjørnøya.
Article
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Quantifying patterns of genetic diversity and differentiation among populations of Arctic birds is funda-mental for understanding past and ongoing population pro-cesses in the Arctic. However, the genetic differentiation of many important Arctic species remains uninvestigated. Here, phylogeography and population genetics were examined in the worldw...
Article
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Oceanographic processes and bathymetric features that consistently aggregate prey are often thought to be the main cues used by planktivorous birds to detect suitable foraging habitat. In this study we aimed to establish the main factors determining the at-sea distribution of the little auk Alle alle, a very abundant seabird in the Arctic during th...
Article
AimExtensive development of human activities in combination with ocean warming is rapidly modifying marine habitats in the Arctic and North Atlantic regions. To understand the potential impacts on marine biodiversity, there is an urgent need to determine distributions and habitat preferences of potentially vulnerable species and to identify sensiti...
Article
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Thyroid hormones affect in vitro metabolic intensity, increase basal metabolic rate (BMR) in the lab, and are sometimes correlated with basal and/or resting metabolic rate (RMR) in a field environment. Given the difficulty of measuring metabolic rate in the field-and the likelihood that capture and long-term restraint necessary to measure metabolic...
Article
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In birds with facultative brood reduction, survival of the junior chick is thought to be regulated primarily by food availability. In black-legged kittiwakes (Rissa tridactyla) where parents and chicks are provided with unlimited access to supplemental food during the breeding season, brood reduction still occurs and varies interannually. Survival...
Article
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Thyroid hormones (TH) are known to stimulate in vitro oxygen consumption of tissues in mammals and birds. Hence, in many laboratory studies a positive relationship between TH concentrations and basal metabolic rate (BMR) has been demonstrated whereas evidence from species in the wild is scarce. Even though basal and field metabolic rates (FMR) are...
Article
1. The ability to store energy endogenously is an important ecological mechanism that allows animals to buffer predictable and unpredictable variation in allostatic load. The secretion of glucocorticoids, which reflects changes in allostatic load, is suggested to play a major role in the adjustment of endogenous stores to these varying conditions....
Article
Full-text available
The function of a foraging trip (self-feeding or provisioning) and the spatial distribution of food resources play an essential role in foraging decisions of central-place foragers. Theory predicts that if foraging patches optimal for self-feeding and provisioning are spatially separated, a bimodal foraging strategy should often be favored. A bimod...
Article
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Climate models predict a multi-degree warming of the North Atlantic in the 21st century. A research priority is to understand the effect of such changes upon marine organisms. With 40 to 80 million individuals, planktivorous little auks Alle alle are an essential component of pelagic food webs in this region that is potentially highly susceptible t...
Article
The purpose of this study was to characterize for the first time seabird diving behavior during bimodal foraging. Little auks Alle alle, small zooplanktivorous Alcids of the High Arctic, have recently been shown to make foraging trips of short and long duration. Because short (ST) and long trips (LT) are thought to occur in different locations and...
Article
The purpose of this study was to characterize for the first time seabird diving behavior during bimodal foraging. Little auks Alle alle, small zooplanktivorous Alcids of the High Arctic, have recently been shown to make foraging trips of short and long duration. Because short (ST) and long trips (LT) are thought to occur in different locations and...
Article
The Atlantic sector of the Arctic is undergoing widespread climate change with increases in air and sea temperatures which impact the timing of ice retreat, snow melt and the development of the marine food web. Dovekies (Alle alle) are small seabirds that migrate to the Atlantic Sector of the Arctic to feed in ice free waters that have abundant lip...
Article
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The goal of this study was to assess how diverse oceanographic conditions and prey communities affect the foraging behavior of little auks Alle alle. The Greenland Sea is characterized by 3 distinct water masses: (1) the East Greenland Current (EGC), which carries Arctic waters southward; (2) the Sorkapp Current (SC), which originates in the Arctic...
Article
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Variation in body size among subpopulations of the same species may reflect phenotypic or genetic responses to environmental gradients or geographical distance. Here, we examine geographical variation in the body size of the dovekie (Alle alle), the most numerous high-Arctic seabird. Locations of dovekie breeding sites are largely restricted to the...
Article
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Tradeoffs between current reproduction and future survival are widely recognized, but may only occur when food is limited: when foraging conditions are favorable, parents may be able to reproduce without compromising their own survival. We investigated these tradeoffs in the little auk (Alle alle), a small seabird with a single-egg clutch. During 2...
Article
Full-text available
Variation in body size among subpopulations of the same species may reflect phenotypic or genetic responses to environmental gradients or geographical distance. Here, we examine geographical variation in the body size of the dovekie (Alle alle), the most numerous high- Arctic seabird. Locations of dovekie breeding sites are largely restricted to th...
Article
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The non-breeding season of seabirds is extremely challenging to study because it is often spent offshore under harsh environmental conditions. We used stable isotope analysis to investigate little auk Alle alle feeding ecology throughout the annual cycle. The geographic distribution of little auks in the Arctic covers a wide range of oceanographic...
Article
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Despite the widespread use of the doubly labelled water (DLW) method in energetic studies of free-ranging animals, effects of the method on study animals are rarely assessed. We studied behavioural effects of two alternative DLW protocols. During two consecutive breeding seasons, 42 parent black-legged kittiwakes received either the commonly used t...
Article
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The maintenance of an effective immune system may entail physiological costs only affordable by individuals in good condition. Some species, like Black-legged Kittiwakes (Rissa tridactyla) in the high arctic, experience important physiological changes during breeding in order to fulfil their reproductive goals. We studied the effects of breeding ef...
Article
The secretion of corticosterone in response to stress is thought to be an adaptive mechanism, which promotes immediate survival at the expense of current reproduction. However, at the individual level, the hypothesis of a corticosterone-related survival appears to be complex. In this study, we tested this hypothesis by combining for the first time...
Article
1. The regulation of energy expenditure in relation to food availability and its consequences for individual fitness in free-ranging animals are poorly understood. Increased daily energy expenditure (DEE) may be viewed as the result of two different processes: expenditure may be forced upwards by low food availability (forcing hypothesis) or enable...
Article
Full-text available
The timing of breeding is a life-history trait that can greatly affect fitness, because successful reproduction depends on the match between the food requirements for raising young and the seasonal peak in food availability. We analysed phenology (hatch dates) in relation to climate change for 2 seabird species breeding in the high-Arctic, little a...
Article
1. The rate at which free-living animals can expend energy is limited but the causes of this limitation are not well understood. Theoretically, energy expenditure may be intrinsically limited by physiological properties of the animal constraining its capacity to process energy. Alternatively, the limitation could be set extrinsically by the amount...
Article
We examined how short-term impacts of experimentally increased foraging effort by one parent reverberate around the family in a monomorphic seabird (little auk, Alle alle), and whether these effects depend on offspring sex. In many species, more effort is required to rear sons successfully than daughters. However, undernourishment may have stronger...
Article
Full-text available
1. An emergency life-history stage is expressed in breeding vertebrates when the immediate survival is threatened by poor energetic conditions (i.e. allostatic overload). This emergency life-history stage shifts energy investment away from reproduction and redirects it toward immediate survival. 2. In birds, this emergency life-history stage is pro...
Article
A bimodal foraging strategy has previously been described for procellariiform seabird species and is thought to have evolved in response to local resource availability being too low for adult birds to meet chick requirements and simultaneously maintain their own body condition. Here, we examine the dual foraging trip pattern of an alcid, the little...
Article
Full-text available
Sexual differences in foraging and provisioning behaviour have been observed in several size-dimorphic seabird species. These differences are usually thought to be driven by size-related mechanisms such as the ability to compete for food or defend the nest. However, recent studies on monomorphic species suggest that sexual differences in foraging m...
Article
1Parental investment strategies are considered to represent a trade-off between the benefits of investment in current offspring and costs to future reproduction. Due to their high residual reproductive value, long-lived organisms are predicted to be more reluctant to increase parental effort.2We tested the hypothesis that breeding little auks (Alle...
Article
Knowledge about the extent to which organisms inhabitating the Arctic are able to adjust to environmental variability is essential in order to predict the impact of future climate change. In this context, the flexibility og two Acrtic-breeding seabirds, the little Auk (Alle alle) and the kittiwake (Rissa tridactyla), in foraging behavior and energy...

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