Age-dependent shaping of the social environment in a long-lived seabird: a quantitative genetic approach.

Individual differences in social behaviour can result in fine-scale variation in spatial distribution and, hence, in the social environment experienced. Given the expected fitness consequences associated with differences in social environments, it is imperative to understand the factors that shape them. One potential such factor is age.

Mercury concentrations in blood and back feathers are repeatable, heritable and correlated in a long-lived seabird.

Mercury pollution is increasing both in the environment and in various organisms, especially top-predators. If variation in individual mercury concentrations is underpinned by genetic among-individual differences in traits related to mercury uptake, storage or excretion, and results in variation in fitness, populations may have the potential to evolve in response to this development. Few studies, however, have been able to collect sufficient information to investigate the genetic basis of pollution levels.

Subjective household poverty as a moderator for the association between employment precariousness and mental health across five european welfare state types.

Objectives: To create better understanding of the mechanisms underlying the association between employment precariousness (EP) and mental health by considering household poverty as a moderator while stratifying for gender across welfare state types (WSTs): Scandinavian, South European, Central- and East European, Bismarckian and Anglo-Saxon.

Methods: Data from the sixth wave of the European Working Conditions Survey (N = 18,725) was used. The Employment Precariousness Scale was used to assess EP on a continuous scale.

Sex- and age-specific mercury accumulation in a long-lived seabird.

Mercury levels in the environment are increasing, such that they are also expected to accumulate in top-predators, but individual-based longitudinal studies required to investigate this are rare. Between 2017 and 2023, we therefore collected 1314 blood samples from 588 individual common terns (Sterna hirundo) to examine how total blood mercury concentration changed with age, and whether this differed between the sexes. Blood mercury concentrations were highly variable, but all exceeded toxicity thresholds above which adverse health effects were previously observed.

Micro-evolutionary response of spring migration timing in a wild seabird.

In the context of rapid climate change, phenological advance is a key adaptation for which evidence is accumulating across taxa. Among vertebrates, phenotypic plasticity is known to underlie most of this phenological change, while evidence for micro-evolution is very limited and challenging to obtain. In this study, we quantified phenotypic and genetic trends in timing of spring migration using 8,032 dates of arrival at the breeding grounds obtained from observations on 1,715 individual common terns () monitored across 27 years, and tested whether these trends were consistent with predictions of a micro-evolutionary response to selection.

Mass mortality among colony-breeding seabirds in the German Wadden Sea in 2022 due to distinct genotypes of HPAIV H5N1 clade 2.3.4.4b.

Mass mortality was observed among colony-breeding seabirds in the German Wadden Sea area of the North Sea during the summer months of 2022. Several species' colonies were affected, most notably sandwich terns (), common terns () and Germany's only northern gannet () colony on the island of Heligoland. Mortality in some tern colonies reached 40%, while other colonies were almost spared.

Mercury contamination level is repeatable and predicted by wintering area in a long-distance migratory seabird.

The environmental presence of mercury has dramatically increased over the past century, leading to increased uptake, especially by top predators such as seabirds. Understanding the exact sources of contamination requires an individual-level approach, which is especially challenging for species that migrate. We took such an approach and located the wintering areas of 80 common terns (Sterna hirundo) through tracking, and, across years, collected feathers grown in those areas to assess their mercury levels using atomic absorption spectrometry.

Contrasting haemoparasite prevalence in larid species with divergent ecological niches and migration patterns.

Haemoparasites represent a diverse group of vector-borne parasites that infect a wide range of vertebrate hosts. In birds, haemoparasite infection rates may be associated with various ecological and life history traits, including habitat choice, colony size and migration distance. Here, we molecularly assessed the prevalence of 3 main haemoparasite genera (, and ) in 2 bird species with different habitat preferences and migratory behaviour: black-headed gulls () and common terns ().

Variation and correlation in the timing of breeding of North Atlantic seabirds across multiple scales.

Timing of breeding, an important driver of fitness in many populations, is widely studied in the context of global change, yet despite considerable efforts to identify environmental drivers of seabird nesting phenology, for most populations we lack evidence of strong drivers. Here we adopt an alternative approach, examining the degree to which different populations positively covary in their annual phenology to infer whether phenological responses to environmental drivers are likely to be (a) shared across species at a range of spatial scales, (b) shared across populations of a species or (c) idiosyncratic to populations. We combined 51 long-term datasets on breeding phenology spanning 50 years from nine seabird species across 29 North Atlantic sites and examined the extent to which different populations share early versus late breeding seasons depending on a hierarchy of spatial scales comprising breeding site, small-scale region, large-scale region and the whole North Atlantic.

The quantitative genetics of fitness in a wild seabird.

Additive genetic variance in fitness is a prerequisite for adaptive evolution, as a trait must be genetically correlated with fitness to evolve. Despite its relevance, additive genetic variance in fitness has not often been estimated in nature. Here, we investigate additive genetic variance in lifetime and annual fitness components in common terns (Sterna hirundo).

High individual repeatability of the migratory behaviour of a long-distance migratory seabird.

Background: Understanding the evolution of migration requires knowledge of the patterns, sources, and consequences of variation in migratory behaviour, a need exacerbated by the fact that many migratory species show rapid population declines and require knowledge-based conservation measures. We therefore need detailed knowledge on the spatial and temporal distribution of individuals across their annual cycle, and quantify how the spatial and temporal components of migratory behaviour vary within and among individuals.

Methods: We tracked 138 migratory journeys undertaken by 64 adult common terns (Sterna hirundo) from a breeding colony in northwest Germany to identify the annual spatiotemporal distribution of these birds and to evaluate the individual repeatability of eleven traits describing their migratory behaviour.

Immunosenescence in the wild? A longitudinal study in a long-lived seabird.

Longitudinal studies of various vertebrate populations have demonstrated senescent declines in reproductive performance and survival probability to be almost ubiquitous. Longitudinal studies of potential underlying proximate mechanisms, however, are still scarce. Due to its critical function in the maintenance of health and viability, the immune system is among the potential (mediators of) proximate mechanisms that could underlie senescence.

Hemispheric asymmetry in ocean change and the productivity of ecosystem sentinels.

Climate change and other human activities are causing profound effects on marine ecosystem productivity. We show that the breeding success of seabirds is tracking hemispheric differences in ocean warming and human impacts, with the strongest effects on fish-eating, surface-foraging species in the north. Hemispheric asymmetry suggests the need for ocean management at hemispheric scales.

How fitness consequences of early-life conditions vary with age in a long-lived seabird: A Bayesian multivariate analysis of age-specific reproductive values.

Evolutionary theory suggests that individuals can benefit from deferring the fitness cost of developing under poor conditions to later in life. Although empirical evidence for delayed fitness costs of poor developmental conditions is abundant, individuals that die prematurely have not often been incorporated when estimating fitness, such that age-specific fitness costs, and therefore the relative importance of delayed fitness costs are actually unknown. We developed a Bayesian statistical framework to estimate age-specific reproductive values in relation to developmental conditions.

Telomere length is heritable and genetically correlated with lifespan in a wild bird.

Telomeres are protective caps at the end of eukaryotic chromosomes that shorten with age and in response to stressful or resource-demanding conditions. Their length predicts individual health and lifespan across a wide range of animals, but whether the observed positive association between telomere length and lifespan is environmentally induced, or set at conception due to a shared genetic basis, has not been tested in wild animals. We applied quantitative genetic "animal models" to longitudinal telomere measurements collected over a 10-year period from individuals of a wild seabird (common tern; Sterna hirundo) with known pedigree.

Understanding the Social Dynamics of Breeding Phenology: Indirect Genetic Effects and Assortative Mating in a Long-Distance Migrant.

AbstractPhenological traits, such as the timing of reproduction, are often influenced by social interactions between paired individuals. Such partner effects may occur when pair members affect each other's prebreeding environment. Partner effects can be environmentally and/or genetically determined, and quantifying direct and indirect genetic effects is important for understanding the evolutionary dynamics of phenological traits.

Telomere length is repeatable, shortens with age and reproductive success, and predicts remaining lifespan in a long-lived seabird.

Telomeres are protective caps at the end of chromosomes, and their length is positively correlated with individual health and lifespan across taxa. Longitudinal studies have provided mixed results regarding the within-individual repeatability of telomere length. While some studies suggest telomere length to be highly dynamic and sensitive to resource-demanding or stressful conditions, others suggest that between-individual differences are mostly present from birth and relatively little affected by the later environment.

Health differences between multiple and single job holders in precarious employment in the Netherlands: A cross-sectional study among Dutch workers.

Introduction: Precarious employment is associated with poor health. Among employees in precarious employment, those with multiple jobs may face additional health risks, e.g.

Age-Specific Offspring Mortality Economically Tracks Food Abundance in a Piscivorous Seabird.

Earlier offspring mortality before independence saves resources for kin, which should be more beneficial when food is short. Using 24 years of data on age-specific common tern (Sterna hirundo) chick mortality, best described by the Gompertz function, and estimates of energy consumption per age of mortality, we investigated how energy wasted on nonfledged chicks depends on brood size, hatching order, and annual abundance of herring (Clupea harengus), the main food source. We found mortality directly after hatching (Gompertz baseline mortality) to be high and to increase with decreasing herring abundance.

Live fast, don't die young: Survival-reproduction trade-offs in long-lived income breeders.

Trade-offs between survival and reproduction are at the core of life-history theory, and essential to understanding the evolution of reproductive tactics as well as population dynamics and stability. Factors influencing these trade-offs are multiple and often addressed in isolation. Further problems arise as reproductive states and survival in wild populations are estimated based on imperfect and potentially biased observation processes, which might lead to flawed conclusions.

Contrasting heterozygosity-fitness correlations across life in a long-lived seabird.

Selection is a central force underlying evolutionary change and can vary in strength and direction, for example across time and space. The fitness consequences of individual genetic diversity have often been investigated by testing for multilocus heterozygosity-fitness correlations (HFCs), but few studies have been able to assess HFCs across life stages and in both sexes. Here, we test for HFCs using a 26-year longitudinal individual-based data set from a large population of a long-lived seabird (the common tern, Sterna hirundo), where 7,974 chicks and breeders of known age were genotyped at 15 microsatellite loci and sampled for life-history traits over the complete life cycle.