Temporal trends in metal pollution: using bird excrement as indicator

Birds as bioindicators of plastic pollution in terrestrial and freshwater environments: A 30-year review

Plastic pollution is a global concern that has grown ever more acute in recent years. Most research has focused on the impact of plastic pollution in marine environments. However, plastic is increasingly being detected in terrestrial and freshwater environments with key inland sources including landfills, where it is accessible to a wide range of organisms. Birds are effective bioindicators of pollutants for many reasons, including their high mobility and high intra- and interspecific variation in trophic levels. Freshwater and terrestrial bird species are under-represented in plastic pollution research compared to marine species. We reviewed 106 studies (spanning from 1994 onwards) that have detected plastics in bird species dwelling in freshwater and/or terrestrial habitats, identifying knowledge gaps. Seventy-two studies focused solely on macroplastics (fragments >5 mm), compared to 22 microplastic (fragments <5 mm) studies. A further 12 studies identified plastics as both microplastics and macroplastics. No study investigated nanoplastic (particles <100 nm) exposure. Research to date has geographical and species' biases while ignoring nanoplastic sequestration in free-living freshwater, terrestrial and marine bird species. Building on the baseline search presented here, we urge researchers to develop and validate standardised field sampling techniques and laboratory analytical protocols such as Raman spectroscopy to allow for the quantification and identification of micro- and nanoplastics in terrestrial and freshwater environments and the species therein. Future studies should consistently report the internalised and background concentrations, types, sizes and forms of plastics. This will enable a better understanding of the sources of plastic pollution and their routes of exposure to birds of terrestrial and freshwater environments, providing a more comprehensive insight into the potential impacts on birds.

Heavy metals in wetlands of southwestern India: from sediments through invertebrates to migratory shorebirds

Heavy metal pollution in Indian wetlands is rising due to industrial, agricultural and urban development activities. Shorebirds occupy upper trophic levels and are therefore especially vulnerable to heavy metal pollution. We evaluated the concentration of heavy metals (zinc, copper, cobalt, chromium, lead and cadmium) in 22 common species of migrant shorebirds (220 shorebird dropping samples) with diverse foraging behaviors, in their different prey (55 prey samples) and in the sediments (90 sediment samples) in different habitat types (mudflats, mangroves and sand beaches) between 2019 and 2021. Further, we analyzed a total of 10 biofilm samples from mudflats and mangroves. We detected relatively low concentrations of heavy metals in the sediments (Zn concentration range: 9.11-40.91 mg/kg; Cu: 5.74-21.38 mg/kg; Co: 2.00-4.04 mg/kg; Cr: 4.05-41.03 mg/kg; Pb: 1.02-7.19 mg/kg; Cd: 0.56-4.35 mg/kg). However, we measured relatively high concentrations of heavy metals in invertebrate prey species (Zn concentration range: 84.72-224.74 mg/kg; Cu: 26.63-170.36 mg/kg; Co: 13.98-14.42 mg/kg; Cr: 14.78-98.16 mg/kg; Pb: 18.95-157.29 mg/kg; Cd: 9.33-60.56 mg/kg). In addition, we found high concentrations of heavy metals in shorebird droppings (Zn concentration range: 41.33-58.8 mg/kg; Cu: 31.42-52.11 mg/kg; Co: 36.34-55.68 mg/kg; Cr: 52.3-68.21 mg/kg; Pb: 25.94-43.13 mg/kg; Cd: 5.53-16.4 mg/kg). It is evident that concentration of heavy metals increased successively moving from sediment to prey to shorebird species, likely through trophic transfer. The biofilm samples contained very high concentrations of Cr, Pb and Cd (22.64, 28.09 and 18.46 mg/kg respectively) which could be harmful to biofilm grazing shorebirds. Since bioaccumulation of heavy metals entail risks in living species, we suggest that increasing concentrations may detrimentally affect physiological processes in invertebrates and shorebirds. There is an urgent need to identify the sources of pollution and to reduce the discharge of heavy metals and other pollutants into coastal and inland wetlands.

Mobile samplers of particulate matter - Flying omnivorous insects in detection of industrial contamination

Flying insects are potential mobile samplers of airborne particulate matter (PM). However, current knowledge on their susceptibility to PM is limited to pollinators. Insects' capacity for particle surface accumulation depends on the lifestyle, structure of the body integuments, and behavioral patterns. Here, we investigate how two species of flying omnivorous insects from the genus Vespula, possessing direct interactions with air, soil, plants, and herbivores, indicate industrial pollution by accumulating coarse (PM₁₀) and fine (PM_2.5) particles on their bodies. The internal accumulation of particles in wasps' gut tissues is assessed considering heavy metals exposure to reveal and discuss the potential magnitude of ecotoxicological risks. Female individuals of Vespula vulgaris and V. germanica were sampled with a hand-netting near to Harjavalta Cu-Ni smelter and in the control areas in southwestern Finland. They were analyzed with light microscopy (LM), electron microscopy (SEM, TEM), and energy-dispersive X-ray spectroscopy (EDX) methods. Near to the smelter, wasps trapped significantly more particles, which were of bigger size and their surface optical density was higher. Vespula vulgaris accumulated larger particles than V. germanica, but that wasn't associated with morphological characteristics such as body size or hairiness. In both areas, accumulated surface PM carried clays and silicates. Only in polluted environments PM consistently contained metallic and nonmetallic particles (from high to moderate weight %) of Fe, Ni, Cu, and S - major pollutants emitted from the smelter. Wasps from industrially polluted areas carried significantly more granules in the columnar epithelial midgut cells. TEM-EDX analyses identified those structures were associated with metal ions such as Cr, Cu, Ni, and Fe. As epithelial gut cells accumulated metal particles, midgut confirmed as a barrier for metal exposure in wasps. External PM contamination in wasps is suggested as a qualitative, yet a natural and simple descriptor of local industrial emissions.

Tissue distribution and association of heavy metal accumulation in a free-living resident passerine bird tree sparrow Passer montanus

Passerine birds have been increasingly used as effective sentinels of ecosystem contamination. They can provide direct evidence of the bioavailability and accumulation of heavy metal elements in the environment. In this study, the bioaccumulation of four heavy metals (Cu, Zn, Pb, and Cd) and Ca in different organs and tissues (feathers, internal organs, skeletons, and muscles) of an urban bird, tree sparrow (Passer montanus), collected from a polluted site [Baiyin (BY)] and a relatively unpolluted site [Liujiaxia (LJX)], and their associations were investigated. There were significantly higher and lower concentrations of heavy metals and Ca, respectively, in different organs and tissues of sparrows in BY than those in LJX. However, except for Pb, the heavy metal levels were below the threshold of sublethal effects. Age-dependent variations in metals were quantified, and it was found that adult bird contained higher concentration of different organs and tissue metals, except for feathers, compared with nestlings and juveniles. The tissue distribution of heavy metals in sparrows of different ages and sex was similar in the two study sites, and heavy metal elements were mainly accumulated in the feathers. This study further investigated the correlation between heavy metals in different organs and tissues and found that the correlations between them were strong in nestlings and adults but weak in juveniles. In addition, Pb and Cd in internal organs, skeletons, and muscles of young sparrows can be estimated using feathers, whereas Cu and Zn were found in adult sparrows. Altogether, our results suggest that tree sparrows will serve as valuable biomonitors of environmental heavy metal pollution and will underscore the importance of tissue types in avian ecotoxicology field studies.

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.

The effect of experimental lead pollution on DNA methylation in a wild bird population

Anthropogenic pollution is known to negatively influence an organism's physiology, behaviour, and fitness. Epigenetic regulation, such as DNA methylation, has been hypothesized as a potential mechanism to mediate such effects, yet studies in wild species are lacking. We first investigated the effects of early-life exposure to the heavy metal lead (Pb) on DNA methylation levels in a wild population of great tits (Parus major), by experimentally exposing nestlings to Pb at environmentally relevant levels. Secondly, we compared nestling DNA methylation from a population exposed to long-term heavy metal pollution (close to a copper smelter), where birds suffer from pollution-related decrease in food quality, and a control population. For both comparisons, the analysis of about one million CpGs covering most of the annotated genes revealed that pollution-related changes in DNA methylation were not genome wide, but enriched for genes underlying developmental processes. However, the results were not consistent when using binomial or beta binomial regression highlighting the difficulty of modelling variance in CpGs. Our study indicates that post-natal anthropogenic heavy metal exposure can affect methylation levels of development related genes in a wild bird population.

Assessment of Heavy Metal Contamination in Excreta of Baya Weaver Bird (Ploceus Philippinus) from Three Districts of Different Zones of Punjab

The objective of the study was to assess the heavy metal contamination in excreta of the Baya Weaver Bird (Ploceus philippinus). Samples were collected from nesting colony sites present in three districts viz. Ludhiana (location I), Ropar (location II) and Ferozepur (location III) falling in Central plain zone, Undulating plain zone and Western plain zone of Punjab respectively. In dry excreta samples fifteen elements were detected through ICAP-AES; As, Pb, Cd, Cr were toxic heavy metals and B, Fe, Cu, Ni, Zn, Mn, Mg, Ca, P, S, Na were essential elements. Toxic heavy metals viz. As (1.88-2.10 ppm), Pb (2.70- 5.25 ppm) and Cr (13.30-23.78 ppm) were found above normal range in excreta collected from studied locations. Statistical analysis showed significant difference among heavy metals and locations which signifies the bioaccumulation of different metals at different locations in excreta of Baya Weaver Bird due to different type of contaminations at studied locations.

Bird Feces as Indicators of Metal Pollution: Pitfalls and Solutions

Bird feces are commonly used as a proxy for measuring dietary metal exposure levels in wild populations. Our study aims to improve the reliability and repeatability of fecal metal measurements and gives some recommendations for sampling. First, we studied levels of variation in metallic element (arsenic, calcium, cadmium, cobalt, copper, nickel, lead) concentrations: temporal variation within an individual, among siblings in a brood and among-brood/spatial variation. Second, we explored the variation caused by dual composition (urate vs. feces) of bird droppings. Two sets of fresh fecal samples were collected from pied flycatcher (Ficedula hypoleuca) nestlings living in a metal polluted area in summers 2017 (dataset 1) and 2018 (dataset 2). We found a great deal of temporal intra-individual variation in metal levels, suggesting that dietary exposure varied markedly in a short time scale (within a day). A sample from only one nestling per brood did not well describe the brood mean value, and we recommend that at least four siblings should be sampled. Brood level samples give relatively good temporal repeatability for most metals. For all the metals, the levels in the fecal portion were more than double to those in the urate portion. Since the mass proportion of urate in the bird droppings varied a great deal among samples, standardizing sampling, e.g., by collecting only the fecal part, would markedly reduce the variation due to composition. Alternatively, urate portion could be used for biomonitoring of internally circulated bioavailable metal.

Assessment of heavy metals in faecal pellets of blue rock pigeon from rural and industrial environment in India

The study was conducted to monitor concentration of six toxic metals in faecal pellets of blue rock pigeon from six industrial areas of Jaipur, i.e. Jhotwara, Malviya, Mansarover, Sitapura, Vishwakarma industrial areas and Sanganer industries, by using atomic absorption spectrophotometer. At the same time, trace metals were also analysed for a reference area so that a comparative impact of the metal pollution from the industries could be figured out. From the data obtained, the highest Cd, Cu, Ni, Pb and Zn concentrations were found in the faecal pellets from Sitapura industrial area (1.12 ± 0.60 μg/g; 128.9 ± 11.10 μg/g; 17 ± 2.87 μg/g; 79.6 ± 42.69 μg/g; 2250 ± 1390.16 μg/g) and the highest Cr (18.6 ± 3.65 μg/g) from Jhotwara industrial area. However, industrial environment has high deposition of studied trace metals (except Ni for Sanganer industries) as compared with reference area. The concentration of Cd was below the detectable level in faecal pellets from reference area. The trend of trace metals from Malviya, Sitapura, Jhotwara and reference areas was noticed as Zn > Cu > Pb > Cr > Ni > Cd and almost same for Sanganer industries and Mansarover industrial area as Zn > Cu > Cr > Pb > Ni > Cd. The excretion of heavy metals in fa1ecal pellets from Vishwakarma industrial area was noticed as Zn > Cr > Cu > Pb > Ni > Cd. Further levels of metals were varied significantly among different industrial areas, P ≤ 0.05, as well as between industrial areas and reference area. The observed high concentration of different heavy metals in faecal pellets of bird species shows their exposure to metal contamination which is warning to spiked environmental pollution.

Weather effects on breeding parameters of two insectivorous passerines in a polluted area

Direct and indirect effects of environmental pollution affect negatively to birds' breeding performance in both urban and industrial environments, but much less is known on how pollution and natural stress factors work together. In our long-term study (1991-2018), we explored whether industrial pollution and associated habitat changes increase the sensitivity of breeding parameters (hatching and fledging success, nestling growth) to temperature and precipitation in two insectivorous bird species, the great tit (Parus major) and the pied flycatcher (Ficedula hypoleuca). We found that both species are rather weather sensitive in terms of their fledging success, but especially in the F. hypoleuca, the negative effect was strengthened in a polluted environment. For both study species, all the breeding parameters, except growth of F. hypoleuca nestlings, were inferior in the polluted area and negatively affected by cold weather. Independent of pollution, the duration of rainy spells during the nestling period had an overall negative effect on fledging success of F. hypoleuca, and this effect became stronger at cold temperatures. The length of rainy spells was, however, positively associated with nestling wing length in both species, possibly because of better availability of some important food resources for wing growth in more humid conditions. The weather-pollution interactions in our study populations were not overwhelmingly strong, but those found in F. hypoleuca show that such interactions exist, they are species-specific and in our study system most likely associated to pollution-related resource (e.g. food) limitation. Higher sensitivity of F. hypoleuca to low temperatures is likely related to its less well-insulated nests and higher dependence on aerial prey, the availability of which is especially reduced during cold and rainy spells. Our study indicates that anthropogenic stress, such as pollution, has synergistic effects with natural stress factors affecting passerine birds' breeding performance.

Facing the threat: common yellowjacket wasps as indicators of heavy metal pollution

We investigated the common wasp, Vespula vulgaris as a bioindicator and biomonitor of metals in the industrial area. Using traps, we collected 257 yellowjackets along a pollution gradient in the Harjavalta Cu-Ni smelter in Southwest Finland. Our method detected metal elements such as arsenic (As), cobalt (Co), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), zinc (Zn), and mercury (Hg) in wasps. The data analyses revealed V. vulgaris can be a proper indicator for As, Cd, Co, Cu, Ni, and Pb, rather than for Fe and Zn contamination. Body burdens of As, Cd, Co, Cu, Ni, and Pb decreased with an increase in distance from smelter. Enrichment factor (EF) followed the pattern Pb ˃ Cd ˃ As ˃ Co ˃ Cu ˃ Ni. The highest bioaccumulation (BAF) values were revealed for Cd (5.9) and the lowest for Pb (0.1). Specially designed software (WaspFacer) allowed revealing body burdens of As, Cd, Co, Cu, Ni, and Pb to be associated with rather smaller than more asymmetric facial colour markings in yellowjackets. These results add to the body of literature on how heavy metal contaminants can have tangible phenotypic effects on insects and open future opportunities for using wasps as indicators of metal pollution.

Relationship between blood test values and blood lead (Pb) levels in Black-headed gull (Chroicocephalus ridibundus: Laridae)

Few studies have evaluated immunosuppression due to lead accumulation below the overt toxicity threshold. If low levels of lead accumulation cause immunosuppression in birds, those birds could become more susceptible to pathogens. We aimed to determine if low levels of lead accumulation lead to immunosuppression in Black-headed gulls (Chroicocephalus ridibundus). Gulls were captured in Tokyo-bay and Mikawa-bay from January to April 2019. Their blood samples were analyzed for eight items. The data were analyzed to evaluate the correlation between lead concentrations and the variables from each bay. Lead was positively correlated with the percentage of heterophils and heterophil and lymphocyte ratio and negatively with lymphocytes. Thus, low lead accumulation levels may induce changes in percentage of the heterophils and lymphocyte.

Female oxidative status in relation to calcium availability, metal pollution and offspring development in a wild passerine

Both Ca deficiency and metal exposure may affect physiological and nutritional condition of breeding females altering their ability to deposit essential resources (e.g. Ca, antioxidants) into the eggs. This effect of the maternal investment into egg quality is not strictly limited to the embryonic period, but may persist after hatching, since nutrient levels in yolks can compromise nestling antioxidant status, growth and fledging success. The goal of this study was to investigate how metal pollution and Ca availability during the breeding season affect oxidative stress biomarkers and plasma biochemistry in adult female pied flycatchers (Ficedula hypoleuca). In addition, we aim to evaluate how maternal antioxidant status and body condition relate to breeding parameters and offspring oxidative balance. Females breeding in a metal-polluted area in SW Finland showed higher metal concentrations compared to the control area, although current levels were below the toxic level able to affect female physiology. In addition, Ca availability was not constraining female oxidative status and general health in the study area. Interestingly, our results suggested that antioxidant response to metals was better when Ca concentrations were high enough to cover the physiological Ca requirements in breeding females. There seems to be a subtle balance between the concentrations of Ca in the organism and the tolerance to metal-related effects that requires further research. This study supports that offspring oxidative balance and nestling development are affected by maternal body condition and antioxidant status.

An Investigation into the Accumulation of Air Borne Trace Metals in the Lungs of Common Myna Acridotheres tristis and Bank Myna Acridotheres ginginianus Captured from Urban and Semi Urban Areas of Lahore and Pattoki, Pakistan

With increasing urbanization and industrialization, clean air is becoming a scarce resource. During the present investigation, concentrations of metals (Pb, Ni and Zn) in the atmosphere and their subsequent deposition in the lungs of two common avian species, common myna, Acridotheres tristis (n = 30) and bank myna, A. ginginianus (n = 20), captured from urban areas of Lahore city and semi-urban areas of Pattoki city 80 km away from main city of Lahore were determined. The obtained results were analyzed statistically using Independent sample t test and Pearson's correlation. A comparison of trace metal concentrations in air of both the cities was also carried out. Statistically, significant variations were recorded for Pb (t (7) = - 4.276, p = 0.001) while non-significant differences were observed for both Ni (t (7) = 0.049, p = 0.962) and Zn (t (7) = 1.555, p = 0.146).

Assessment of Pb and Cd contaminations in the urban waterway sediments of the Nen River (Qiqihar section), Northeastern China, and transfer along the food chain

The increasing anthropogenic inputs of Pb and Cd into China's Nen River (Qiqihar section) owing to rapid urbanization in the past 50 years may pose ecological risks to the river's aquatic system. To confirm this hypothesis, we determined the Pb and Cd concentrations in the sediments of the Nen River flowing across Qiqihar City by comparing the control group (samplings in the Nen River branch bypassing the city) and bioaccumulation along the food chain. We found significantly higher Pb concentrations in the sediments than in the control group (39.21 mg kg^-1 dry weight [dw] vs. 22.44 mg kg^-1 dw; p < 0.05). However, the difference between the Cd contents of the two groups was nonsignificant (0.33 mg kg^-1 dw vs. 0.30 mg kg^-1 dw) (p = 0.07). Accumulated Pb and Cd in the sediments pose a medium risk to the system of Nen River according to the result of risk assessment code analysis. The increased Pb and Cd levels along the food chain had adverse health effects in the species at the top level of the food chain. For example, the feathers of Corvus frugilegus and Sterna hirundo contained 0.28-2.25 mg kg^-1 dw of Cd. These values are considered potentially toxic to common avian species. The bone Pb level of C. frugilegus ranged from 4.82 to 7.41 mg kg^-1 dw within the increasing Pb range (2-15 mg kg^-1 dw) of common water birds. The inputs of Pb and Cd into the local environment should be reduced for the preservation of aquatic system health.

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.

Trace element exposure of whooper swans (Cygnus cygnus) wintering in a marine lagoon (Swan Lake), northern China

Trace element poisoning remains a great threat to various waterfowl and waterbirds throughout the world. In this study, we determined the trace element exposure of herbivorous whooper swans (Cygnus cygnus) wintering in Swan Lake (Rongcheng), an important swan protection area in northern China. A total of 70 samples including abiotic factors (seawater, sediments), food sources (seagrass, macroalgae), feathers and feces of whooper swans were collected from the marine lagoon during the winters of 2014/2015 and 2015/2016. Concentrations of Cu, Zn, Pb, Cr, Cd, Hg and As were determined to investigate the trace element exposure of whooper swans wintering in the area. Results showed that there was an increasing trend in sediment trace element concentrations, compared with historical data. The trace element concentrations in swan feces most closely resembled those of Zostera marina leaves, especially for Cd and Cr. The Zn and Hg concentrations in the swan feces (49.57 and 0.01mg/kg, respectively) were lower than the minimum values reported in the literature for other waterfowls, waterbirds and terrestrial birds. However, the concentrations of the other five trace elements fell within the lower and mediate range of values reported for birds across the world. These results suggest that the whooper swans wintering in Swan Lake, Rongcheng are not suffering severe trace element exposure; however, with the increasing input of trace elements to the lagoon, severe adverse impacts may occur in the future, and we therefore suggest that the input of trace elements to this area should be curbed.

Vitamin profiles in two free-living passerine birds under a metal pollution gradient - A calcium supplementation experiment

Vitamin and carotenoid deficiency may impair development in free-living vertebrates, because of the importance of these micronutrients to growth, antioxidant defense and calcium regulation. Micronutrient and calcium insufficiency can be intensified by metal pollution which can interfere with nutrient homeostasis or indirectly reduce food availability. Furthermore, absorption of dietary heavy metals is dependent on food calcium and vitamin levels. We investigated the effect of calcium on plasma vitamin and carotenoid profiles and how these affected growth and survival in two passerine birds with different calcium turnover living along a metal pollution gradient. Vitamins (A, D₃ and E) and carotenoids were quantified from blood plasma of great tit (Parus major) and pied flycatcher (Ficedula hypoleuca) nestlings. Metal concentrations in soil and in feces from the same nestlings were used to assess the exposure to air pollution. Additionally, we examined the vitamin level variation between developmental stages (eggs and nestlings within the same brood). Our results showed that generally higher concentrations of vitamins and carotenoids circulate in blood of great tits than in pied flycatchers. In general, birds inhabiting the polluted zone presented lower concentrations of the studied micronutrients. Calcium supplementation and metal pollution decreased vitamin A concentration in pied flycatcher, but not in great tit, while vitamin A affected growth and survival in great tit and pied flycatcher respectively. Our results suggest that populations under exposure to metal pollution may experience increased vitamin A deficiency, and that the two passerine species, while obtaining similar micronutrients in food, respond differently to environmental disturbance of nutrients.

Corticosterone levels in relation to trace element contamination along an urbanization gradient in the common blackbird (Turdus merula)

In a rapidly urbanizing world, trace element pollution may represent a threat to human health and wildlife, and it is therefore crucial to assess both exposition levels and associated effects of trace element contamination on urban vertebrates. In this study, we investigated the impact of urbanization on trace element contamination and stress physiology in a wild bird species, the common blackbird (Turdus merula), along an urbanization gradient (from rural to moderately urbanized areas). Specifically, we described the contamination levels of blackbirds by 4 non-essential (Ag, Cd, Hg, Pb) and 9 essential trace elements (As, Co, Cr, Cu, Fe, Mn, Ni, Se, Zn), and explored the putative disrupting effects of the non-essential element contamination on corticosterone levels (a hormonal proxy for environmental challenges). We found that non-essential trace element burden (Cd and Pb specifically) increased with increasing urbanization, indicating a significant trace element contamination even in medium sized cities and suburban areas. Interestingly, the increased feather non-essential trace element concentrations were also associated with elevated feather corticosterone levels, suggesting that urbanization probably constrains birds and that this effect may be mediated by trace element contamination. Future experimental studies are now required to disentangle the influence of multiple urban-related constraints on corticosterone levels and to specifically test the influence of each of these trace elements on corticosterone secretion.

Effects of dietary lead exposure on vitamin levels in great tit nestlings - An experimental manipulation

Exposure to metal pollution negatively affects animal physiology, including nutrient metabolism, but in the wild an effect can seldom be attributed to a single metal. Moreover, little is known about how the metabolism of vitamins, essential micronutrients for developing juveniles, is affected by toxic metals. Therefore we experimentally investigated the effects of lead (Pb), a widespread toxic metal, on four fat-soluble vitamins A (total and retinol), D3, E (total and α-tocopherol) and K and carotenoids (lutein, zeaxanthin and unidentified) in great tit (Parus major) nestlings. In addition to a control group where no Pb was provided, two Pb-dosed groups were compared to a metal exposed group in the vicinity of a Ni-Cu smelter. We examined whether Pb treatment affects vitamin homeostasis and how the response of Pb-treated birds relates to that of a population under industrial exposure of Pb and other metals. For this purpose, vitamin and carotenoid levels were quantified with UPLC-MS from plasma of 7 days-old nestlings. All metal exposed groups showed increased vitamin A and retinol levels. However, vitamin levels were not directly associated with fecal Pb levels, with the exception of retinol, which was positively correlated with fecal Pb. Alpha-tocopherol, lutein and zeaxanthin levels were positively associated with body mass and wing growth rate. To conclude, Pb exposure increased plasma vitamin A and retinol levels while the levels of other vitamins and carotenoids rather reflected secondary pollution effects via differences in habitat and diet quality at the smelter site. Our findings suggest Pb exposed nestlings may allocate the vitamins needed for growth and development to fight the physiological stress thus compromising their fitness.

Effects of calcium supplementation on growth and biochemistry in two passerine species breeding in a Ca-poor and metal-polluted area

Several studies provide evidence of calcium (Ca)-limited reproduction in birds. A Ca-supplementation experiment was carried out in 2014 in a Ca-poor area associated with metal pollution in SW Finland. We aimed to evaluate the relationship between Ca availability and heavy metal exposure in free-living passerines, and to compare Ca levels in plasma and feces and the effects of Ca supplementation and metals on breeding, nestling growth, and plasma biochemistry in great tits and pied flycatchers. Although the Ca supplement was used by parents, in general the treatment had limited effects on growth and biochemistry, suggesting that parents are capable of finding sufficient Ca-rich foods to allow nestlings to grow properly. Snail shells were an abundant Ca source in the moderately polluted zone for pied flycatcher, and great tits likely combines the intake of snail shells and other anthropogenic Ca-rich items. Great tits had higher Ca concentrations in feces and plasma than pied flycatcher nestlings, suggesting that they need and sustain higher Ca levels and seem to be more opportunistic in search for Ca than pied flycatcher, since they consumed more of the supplemented Ca. Negative effects of pollution in nestling size and fledgling number were found in great tit. This species may suffer especially from the lower food quality and quantity in the polluted area. The pied flycatcher seems to be adapted to low Ca availability and they can successfully breed when metal concentrations are not too high. Our results show that great tits and pied flycatchers may employ different strategies in response to low Ca availability.

Tracking pan-continental trends in environmental contamination using sentinel raptors-what types of samples should we use?

Biomonitoring using birds of prey as sentinel species has been mooted as a way to evaluate the success of European Union directives that are designed to protect people and the environment across Europe from industrial contaminants and pesticides. No such pan-European evaluation currently exists. Coordination of such large scale monitoring would require harmonisation across multiple countries of the types of samples collected and analysed-matrices vary in the ease with which they can be collected and the information they provide. We report the first ever pan-European assessment of which raptor samples are collected across Europe and review their suitability for biomonitoring. Currently, some 182 monitoring programmes across 33 European countries collect a variety of raptor samples, and we discuss the relative merits of each for monitoring current priority and emerging compounds. Of the matrices collected, blood and liver are used most extensively for quantifying trends in recent and longer-term contaminant exposure, respectively. These matrices are potentially the most effective for pan-European biomonitoring but are not so widely and frequently collected as others. We found that failed eggs and feathers are the most widely collected samples. Because of this ubiquity, they may provide the best opportunities for widescale biomonitoring, although neither is suitable for all compounds. We advocate piloting pan-European monitoring of selected priority compounds using these matrices and developing read-across approaches to accommodate any effects that trophic pathway and species differences in accumulation may have on our ability to track environmental trends in contaminants.

Long-term recovery of clutch size and egg shell quality of the pied flycatcher (Ficedula hypoleuca) in a metal polluted area

We explored if breeding parameters and egg shell quality of an insectivorous passerine, pied flycatcher Ficedula hypoleuca, have fully recovered after c.a. 99% decrease in dust emissions from a non-ferrous smelter in the course of the 23 year study period. Some potentially important population characteristics (density, phenology, age) and environmental variables (habitat, inter-specific competition) were taken into account in the analysis. We found marked increase in reproductive parameters (egg shell quality, clutch size, hatchability, and fledgling number) in the metal polluted area especially in 1990's when metal-rich dust emissions from the smelter were markedly reduced. Still clutch sizes and fledgling numbers remain below the levels of the reference area. There is currently very little evidence of direct toxic effects of metals in our study population but full recovery of breeding parameters may not be reached until the full recovery of food chains, which is likely to be a slow process.