Local survival of pied flycatcher males and females in a pollution gradient of a Cu smelter

Does microplastic exposure and sex influence shell selection and motivation in the common European hermit crab, Pagurus bernhardus?

Microplastics (<5 mm) are a threat to marine biodiversity however their effects on animal cognition and behaviour are unclear. We investigated whether microplastic exposure affects shell selection behaviour and motivation in the common European hermit crab, Pagurus bernhardus. Subjects were maintained for 5 days in tanks containing either: polyethylene microplastic spheres (n = 40), or no plastic (n = 40). They were then placed in low-quality shells and presented with an alternative high-quality shell. When they first touched the high-quality shell, the hermit crabs were startled using visual and aural stimuli. We recorded the post-startle latency to re-contact the high-quality shell, quantifying motivation to explore and acquire a better shell. Plastic-exposed females were more likely to select the high-quality shell than control females. As hypothesised, female hermit crabs had longer initial contact latencies, startle durations, and shell entry latencies than males. We also found an interaction effect on shell investigation duration: females from the control treatment spent longer investigating the high-quality shell compared to males. This was absent in the microplastic treatment with females behaving similar to males. This controlled study serves as a starting point to investigate the effects of microplastics and sex differences on behaviour when under predatory threat, and demonstrated sex dependent sensitivity to an environmental pollutant of global concern.

Improved breeding parameters in the pied flycatcher with reduced pollutant emissions from a copper smelter

In recent decades, industrial emissions have been reduced in many countries, which provides an opportunity for the recovery of polluted ecosystems. However, our knowledge of the rate and factors facilitating the recovery of local bird populations after pollution abatement is incomplete. Long-term (1989-2021) annual observations on nest-box populations of a passerine bird, Ficedula hypoleuca, were used to analyze temporal dynamics of breeding parameters following a 50-fold reduction of industrial emissions from the Middle Ural copper smelter (MUCS) according to pollution zone, habitat, air temperature, and breeding density. In the heavily polluted (impact) zone (1-2 km of MUCS), egg and fledgling production were strongly impaired compared to the moderately polluted (buffer zone, 4-8 km of MUCS) and unpolluted control zone (16-27 km of MUCS). During the study period, the laying date advanced along with increasing spring air temperatures. The clutch size increased in the impact zone by 26%, in the buffer zone by 10%, and in control by 5%. The number of fledglings increased in the impact zone by 102% and the buffer zone by 17%. In the most recent year (2021), mean laying date, clutch size, fledgling production, and the frequency of nests with unhatched eggs in the impact zone did not reach the control level, whereas the frequency of nests with perished chicks did not differ among zones. Breeding parameters of birds in the impact zone improved slowly, likely due to the slow recovery of habitats. We conclude that bird reproduction may require many decades to recover fully in the heavily polluted zone.

Trophic match/mismatch and reproduction of the pied flycatcher Ficedula hypoleuca in a metal-polluted area

In polluted areas, birds can suffer from changes in diet composition and inferior food quality. It is unknown if pollution can desynchronize the phenology of birds and their prey, resulting in a mismatch between food demand and availability. For 2 years, we studied seasonal changes in the biomass of leaf-eating invertebrates and the timing of reproduction and breeding success of an insectivorous bird, the pied flycatcher, in an area heavily polluted by the Middle Ural copper smelter and in an unpolluted control area. Seasonal variations in herbivore biomass were relatively synchronous in polluted and unpolluted areas, whereas birds started breeding later in the polluted area. In the year with an earlier spring, the herbivore peak was early and short, resulting in lower food availability for birds feeding nestlings. The greater the mismatch between food demand and availability the higher was the frequency of nests containing perished nestlings and the lower the body mass of fledglings. Our data did not support the hypothesis that the detrimental effect of the trophic mismatch on birds is greater in the polluted area than in the unpolluted one. Nevertheless, delayed breeding in the pied flycatcher in polluted areas suggests a higher probability of mistimed bird reproduction in the years with a short period of food abundance. Thus, the synchrony of phenology of birds and their prey is an important pollution-related factor that should be taken into account when analyzing the effects of pollution on birds.

Investigating temporal and spatial correlates of the sharp decline of an urban exploiter bird in a large European city

Increasing urbanisation and human pressure on lands have huge impacts on biodiversity. Some species, known as “urban exploiters”, manage to expand in urban landscapes, relying on human resources. The House Sparrow (Passer domesticus) is the perfect example of a human-commensal species. Surprisingly, this urban exploiter has been declining all over Europe over the past decades. The proximate causes of this decline remain poorly understood. We particularly lack understanding about urban habitat characteristics that are particularly unfavourable for House Sparrows. In the present study, we analysed fine-scale habitat characteristics of House Sparrow population sizes and trends using a fifteen-year House Sparrow census (2003–2017) covering the urban diversity of Paris (nearly 200 census sites), one of the densest European cities. We documented for the first time the dramatic decline (−89%) of the species in Paris over the study period. The temporal decline over the whole city correlates with the concomitant increase in the number of breeding Sparrowhawks. We could not detect statistical influences of annual variations in weather conditions and pollution. The decline of House Sparrows is spatially heterogeneous. Indeed, site-scale analyses revealed sharpest declines at sites that initially hosted the largest numbers of sparrows, which are areas with a relatively high proportion of green spaces and new buildings. Further experimental studies are now needed to disentangle the exact impact of specific characteristics of the urban environment on House Sparrow populations.

Exposure to Pb impairs breeding success and is associated with longer lifespan in urban European blackbirds

Although several factors have been highlighted to explain the influence of urbanization on bird fitness and survival, the role of persistent toxicants such as lead (Pb), which is typically present in urban areas worldwide, has seldom been studied despite the ecological importance of such a widespread stressor. Studying free-living European blackbirds (Turdus merula) in city parks, we tested the hypothesis that low-dose chronic exposure to Pb could shape the life-history traits of urban birds. The feather concentrations of Pb and cadmium were typical of urban areas and low-to-moderate contamination of sites. Although the lifetime breeding success of females decreased with increasing exposure to Pb, the lifespan and survival probabilities of blackbirds increased with Pb contamination regardless of gender. Breeding effort-dependent patterns in the relationship between lifespan and Pb levels were highlighted. No significant relationships were detected between cadmium and life-history traits. The results suggest a possible trade-off between self-maintenance and reproduction, with the most affected birds redirecting allocations towards their own survival, which is consistent with the “stress hormone hypothesis”. These findings suggest that Pb pollution in urban environments may shape avian ecological features and be one of the drivers of wildlife responses to urbanization and that some urban areas may function as ecological traps driven by pollutants.

Interspecific variation in the spatially-explicit risks of trace metals to songbirds

Many wild animals can be adversely affected by trace metals around point sources but little is known about the risks to birds across their ranges. Trace metals in the soil are ubiquitously, if heterogeneously distributed, across the world due to natural and anthropogenic sources. Here, we built, parameterized and applied a spatially explicit modelling framework to determine the risks of soil-associated metals to 30 invertebrate-consuming passerine species across their spatial distribution in England and Wales. The model uses a risk characterization approach to assess the risks of soil-associated metals. Various monitoring datasets were used as input parameters: soil metal concentrations in England and Wales, bird spatial distribution; bird diet, bioaccumulation and toxicity data were extracted from the literature. Our model highlights significant differences in toxicity risks from Cd, Cu, Pb and Zn across the UK distributions of different species; Pb and Zn posed risks to all species across most of species' distributions, with more localised risks to some species of conservation concern from Cd and Cu. No single taxa of invertebrate prey drove avian exposure to metal toxicity. Adults were found to be at higher risk from Pb and Zn toxicity across their distributions than nestlings. This risk was partially driven by diet, with age differences in diets identified. Our spatially explicit model allowed us to identify areas of each species' national distribution in which the population was at risk. Overall, we determined that for all species studied an average of 32.7 ± 0.2%, 8.0 ± 0.1%, 86.1 ± 0.1% and 93.2 ± 0.1% of the songbird spatial distributions in the UK were characterized at risk of Cd, Cu, Pb and Zn, respectively. Despite some limitations, our spatially explicit model helps in understanding the risks of metals to wildlife and provides an efficient method of prioritising areas, contaminants and species for environmental risk assessments. The model could be further evaluated using a targeted monitoring dataset of metal concentration in bird tissues. Our model can assess and communicate to stakeholders the potential risks of environmental contaminants to wildlife species at a national and potentially international scale.

Temporal trends in metal pollution: using bird excrement as indicator

Past mining and smelting activities have resulted in metal polluted environments all over the world, but long-term monitoring data is often scarce, especially in higher trophic levels. In this study we used bird (Parus major and Ficedula hypoleuca) excrement to monitor metal pollution in the terrestrial environment following 16 years of continuously reduced emissions from a copper/nickel smelter in Finland. In the early 1990s, lead and cadmium concentrations dropped significantly in excrement, but the reduction did not directly reflect the changes in atmospheric emission from the smelter. This is likely due to a continuous contribution of metals also from the soil pool. We conclude that bird excrement can be used to assess changes in the environment as a whole but not specifically changes in atmospheric emission. Inter-annual variation in excrement concentration of especially copper and nickel demonstrates the importance of long-term monitoring to discern significant trends.

Persistent organic pollution in a high-Arctic top predator: sex-dependent thresholds in adult survival

In long-lived species, any negative effect of pollution on adult survival may pose serious hazards to breeding populations. In this study, we measured concentrations of various organochlorines (OCs) (polychlorinated biphenyl and OC pesticides) in the blood of a large number of adult glaucous gulls (Larus hyperboreus) breeding on Bjørnøya (Bear Island) in the Norwegian Arctic, and modelled their local survival using capture-recapture analysis. Survival was negatively associated with concentrations of OCs in the blood. The effect of OCs was nonlinear and evident only among birds with the highest concentrations (the uppermost deciles of contamination). The threshold for depressed survival differed between the sexes, with females being more sensitive to contamination. For birds with lower OC concentration, survival was very high, i.e. at the upper range of survival rates reported from glaucous and other large gull species in other, presumably less contaminated populations. We propose two non-exclusive explanations. First, at some threshold of OC concentration, parents (especially males) may abandon reproduction to maximize their own survival. Second, high contamination of OC may eliminate the most sensitive individuals from the population (especially among females), inducing a strong selection towards high-quality and less sensitive phenotypes.

Breeding performance of blue tits (Cyanistes cæruleus ultramarinus) in relation to lead pollution and nest failure rates in rural, intermediate, and urban sites in Algeria

The breeding parameters and the egg and nestling morphology of Cyanistes caeruleus populations from rural, intermediate, and urban sites in Algeria and the relationships of those variables with lead contamination were studied during three consecutive years. Breeding success was explained only by predation and vandalism rates. Predation was higher in the rural area, whereas vandalism was higher in the urban site. The other measured breeding parameters and egg characteristics were relatively insensitive to study site. The morphology of urban nestlings exhibited a trend toward smaller body size and mass compared to individuals from intermediate and rural sites. Although lead concentrations were higher in the tissues of urban birds than in intermediate and rural individuals, we did not detect a clear influence of this variable on nestling morphology. We conclude that urbanization influenced blue tit breeding parameters through predation and vandalism and nestling morphology through mechanisms other than lead pollution.

Adult tree swallow survival on the polychlorinated biphenyl-contaminated Hudson River, New York, USA, between 2006 and 2010

The upper Hudson River basin in east central New York, USA, is highly contaminated, primarily with polychlorinated biphenyls (PCBs). Reduced adult survival has been documented in tree swallows (Tachycineta bicolor) at a similarly PCB-contaminated river system in western Massachusetts. The purpose of the present study was to assess whether adult survival of tree swallows was likewise affected in the Hudson River basin. Between 2006 and 2010, a total of 521 female tree swallows were banded, of which 148 were retrapped at least once. The authors used Program MARK and an information theoretic approach to test the hypothesis that PCB contamination reduced annual survival of female tree swallows. The model that best described the processes that generated the capture history data included covariate effects of year and female plumage coloration on survival but not PCB/river. Annual survival rates of brown-plumaged females (mostly one year old) were generally lower (mean phi=0.39) than those of blue-plumaged females (mean phi=0.50, one year or older). Poor early spring weather in 2007 was associated with reduced survival in both plumage-color groups compared to later years. Models with the effects of PCB exposure on survival (all ΔAICc values >5.0) received little support.

Metal pollution does not bias offspring sex ratio in great tit (Parus major)

PURPOSE

We measured offspring sex ratios in a resident insectivorous passerine bird, the Great tit Parus major, to find out whether metal pollution around a Finnish copper smelter would bias sex ratios in this territorial forest bird species. Besides a direct effect of pollutants, we were interested in possible indirect effects of pollution-related resource limitation, i.e., changes in food quality and quantity, on sex ratio.

METHODS

We manipulated the diet quantity and quality (carotenoid levels) of P. major nestlings in polluted and unpolluted environments to find out if variation in dietary resource levels has any effect on fledgling sex ratios. Faecal metal levels of nestlings were analysed to monitor the level of pollution exposure at each territory. Near the time of fledging (at the age of 15 days), feather samples were collected for molecular sex determination.

RESULTS

We did not find any association between metal exposure levels and offspring sex ratio, and thus, our results do not support the hypothesis that metal pollution would have direct effects on P. major offspring sex ratio. We found that, irrespective of pollution level, high nestling mortality was associated with male-biased sex ratio, most likely due to sex-specific mortality. Our feeding treatment, however, showed no significant effects on offspring sex ratio, possibly because natural variation in food availability outweighed the effect of our food manipulation on nestling mortality.

CONCLUSIONS

We conclude that metal exposure at the levels found in our study area does not bias fledgling sex ratios in this species, but biased sex ratios may follow under natural or pollution-related resource limitation.

Pollution and its impact on wild animals: a meta-analysis on oxidative stress

Oxidative stress is the unifying feature underlying the toxicity of anthropogenic pollution (e.g., heavy metals, polycyclic aromatic hydrocarbons, and nitrogen-oxides) and the ultimate culprit in the development of many diseases. Yet, there has been no attempt to summarize the published data on wild terrestrial animals to reveal general trends regarding the effects of pollution on oxidative stress. The main findings of this meta-analysis reveal that, as predicted, there is an overall increase in oxidative stress when exposed to pollution. This is mainly due to a weak overall increase of oxidative damages, although there is some variation across taxa. The reduced form of glutathione (GSH) and its associated enzymes are the most reliable biomarkers. This result is important when choosing biomarkers and when using less-invasive sampling of endangered species, or for longitudinal approaches. To be able to predict future population outcomes, possible treatments, but also evolutionary responses to a changing environment, a greater integration of biotic factors such as temperature, bioavailability of toxic elements, and species-specific responses are needed.