Razorbills (Alca torda) as bioindicators of mercury pollution in the southwestern Mediterranean

Dynamics and effects of plastic contaminants' assimilation in gulls

Polybrominated diphenyl ethers are persistent disrupters assimilated by organisms, yet little is known about their link to plastic ingestion and health effects. In an experiment, two groups of yellow-legged/lesser black-backed gulls (Larus michahellis/Larus fuscus) were fed plastics with BDE99 to assess leaching into brain, preen oil, liver and fat tissues and evaluate effects on health and stress parameters. Although most plastic was regurgitated, we observed a clear relation between plastic ingestion and chemical leaching. BDE99 exhibited higher levels in brain tissue of gulls from the plastic groups. Also, only values of cholinesterases measured in plasma were significantly reduced in the 'plastic' groups. Cholinesterase activity in the brain also tended to decrease, suggesting a negative effect in gulls' neurofunction. Results indicate that chemical leaching occurs, even when plastics stay in the stomach for a short period of time and showed that this can affect gulls' health.

Metal concentrations in feathers of red-legged cormorants (Phalacrocorax gaimardi) and sources of plastic in a nesting colony from northern Chile

Mining industry is increasing the concentrations of heavy metals in coastal ecosystems of northern Chile. The presence of plastic in the nests of red-legged cormorants could be acting as a vector of metal presence in their organism. Here we analyze the source of plastic in the nests of cormorants by characterizing the abundance and type of marine debris in beaches and sea surface and the concentrations of eight metals in their feathers. Plastic was present in overall sampled nests and floating and beach debris are not the main sources of plastic to the nests. Overall analyzed metals were present in the cormorants in the following order: Zn > Cu > Se > Pb > Cd > As > Hg > Cr and Se, Cd and Pb concentrations were above the toxic limit. Further studies should investigate the potential adverse effects that plastics and metals presence may cause in this nesting colony.

The Total Mercury Concentration in Organs of Eurasian Magpies (Pica pica) and Common Woodpigeons (Columba palumbus) from the Warsaw Municipal Area

Mercury is a toxic element widely distributed in the natural environment, affecting animals' health. It is released into the environment from both natural and anthropogenic sources. The present study analyzed the mercury concentrations in liver, kidney, heart and muscle tissue in two species of birds from the Warsaw area, which were used as bioindicators of local environmental pollution with this metal. The mercury content in the examined samples was determined using atomic absorption spectrometry (AAS) utilizing automatic mercury analyzer type AMA 254. The highest mercury content was found in the body of Eurasian magpies, in which it was 0.025; 0.021; 0.006; 0.0037 and 0.029 mg kg-1 of tissue wet weight for kidney, liver, heart, thigh muscles and pectoral muscles, respectively. In the case of common woodpigeons, the content of this metal was significantly lower, amounting to 0.007; 0.005; 0.002; 0.001 and 0.001 mg∙kg-1 wet weight for kidney, liver, heart, thigh muscles and pectoral muscles, respectively. In light of data from the available literature, the values obtained should be considered low, not causing a risk to animal health. The results obtained indicate low environmental exposure to this element.

A Review of Non-Invasive Sampling in Wildlife Disease and Health Research: What’s New?

Simple Summary

The interest in wildlife research has increased in the last decades as more scientists work within a One Health framework that regards human, livestock and wildlife health as connected entities. To minimise the impact of research on wildlife, collecting samples with as little disturbance of the animals as possible is important. In our review, we assess the use of so-called non-invasive sampling and summarise which samples can be used successfully when carrying out research on wildlife diseases and health status. Our results show that interest in minimally invasive sampling has steadily increased since the 2010s. Topics able to employ these methods include disease research, but also stress and other hormone assessments, pollution studies, and dietary studies. At the moment, such methods are mainly used to collect samples from land mammals, however, they can also be used in a wide range of other animals. Ever more capable analytical methods will allow for an even wider use of such “animal-friendly” sampling methods.

Abstract

In the last decades, wildlife diseases and the health status of animal populations have gained increasing attention from the scientific community as part of a One Health framework. Furthermore, the need for non-invasive sampling methods with a minimal impact on wildlife has become paramount in complying with modern ethical standards and regulations, and to collect high-quality and unbiased data. We analysed the publication trends on non-invasive sampling in wildlife health and disease research and offer a comprehensive review on the different samples that can be collected non-invasively. We retrieved 272 articles spanning from 1998 to 2021, with a rapid increase in number from 2010. Thirty-nine percent of the papers were focussed on diseases, 58% on other health-related topics, and 3% on both. Stress and other physiological parameters were the most addressed research topics, followed by viruses, helminths, and bacterial infections. Terrestrial mammals accounted for 75% of all publications, and faeces were the most widely used sample. Our review of the sampling materials and collection methods highlights that, although the use of some types of samples for specific applications is now consolidated, others are perhaps still underutilised and new technologies may offer future opportunities for an even wider use of non-invasively collected samples.

Feather mercury levels in beached Magellanic penguin (Spheniscus magellanicus) in northern Argentina during the non-breeding season

Mercury (Hg) is a great concern for marine environments. Bird feathers have been widely used to assess Hg pollution. In this study, we determine mercury concentrations in body feathers of juvenile Magellanic penguins (Spheniscus magellanicus) from the southeastern sector of Buenos Aires province, Argentina, during a non-breeding season, considering both sexes. Hg levels, considering both females and males together, ranged between 265.5 and 1515.52 ng/g. These levels are well below the concentrations in feathers suggested for taking actions focused on the protection of seabirds. Non-significant differences between sexes regarding Hg levels were found, probably because juveniles were sexually immature and females did not excrete Hg by egg laying yet. Hg concentrations found in this study were an order of magnitude higher than those reported 10 years ago for the species in breeding areas on the Argentine coast. Thus, the present study provides relevant information indicating a possible increase of Hg pollution in the southwestern region of the Atlantic Ocean and thus trigger for the development of monitoring programs and regional strategies to improve the conservation status of this species.

Distribution paths of endocrine disrupting phenolic compounds in waterbirds (Mergus merganser, Alca torda, Clangula hyemalis) from the Southern Baltic

This study determined the distribution of phenol derivatives in the organisms of waterbirds and the factors influencing their bioaccumulation and affinity to specific tissues. Concentrations of bisphenol A (BPA), 4-tert-octylphenol (4-t-OP) and 4-nonylphenol (4-NP) were determined in the brains, subcutaneous fat, kidneys, livers and pectoral muscles of goosanders Mergus merganser (GO), long-tailed ducks Clangula hyemalis (LO) and razorbills Alca torda (RA). The birds came from the winter by-catch (2014-2016) in the Southern Baltic. Different distribution routes of individual phenol derivatives in the birds were established, most likely due to their ability to bind to proteins and/or dissolve in lipids. BPA and 4-NP accumulated most in the muscles (BPA <2.0-223.0 ng^.g^-1 dw, 4-NP 26.0-476.4 ng^.g^-1 dw), livers (BPA <2.0-318.2 ng^.g^-1 dw, 4-NP 60.7-525.8 ng^.g^-1 dw), and kidneys (BPA <2.0-836.1 ng^.g^-1 dw, 4-NP 29.3-469.2 ng^.g^-1 dw), while 4-t-OP was stored mainly in the brains (2.6-341.1 ng^.g^-1 dw), subcutaneous fat (0.7-173.7 ng^.g^-1 dw) and livers (<0.5-698.8 ng^.g^-1 dw). The liver was the only organ where all compounds showed a positive correlation with each other and alkylphenols were also positively correlated with each other in tissues with high fat content (brains and subcutaneous fat), and negatively in muscles. Despite the different trophic levels of birds, the concentrations of phenol derivatives in the tissues between individual species in most cases did not differ significantly. However, between the species on a similar trophic level, the higher biomagnification coefficient was calculated for LO feeding on benthos, and the lower for RA feeding on pelagic fish (p < 0.05). The good condition of birds, resulting in large intestinal fat stores, promoted on the one hand the penetration of phenol derivatives from the intestine to the liver, and on the other hand their accumulation in subcutaneous fat, thereby protecting the brain.

Seabird droppings: Effects on a global and local level

Seabirds, with approximately 1 billion specimens, are the main exchangers of nutrients between Terrestial and Marine Systems and they have become an emerging interest group because of their effects on the planet's ecosystem. This review paper aims to highlight the impact of seabird droppings at different trophic levels, their occurrence, ecological risks and effects on soil, water, atmosphere and biota at global and local level to try to understand the ecological and climatic changes associated with the activities of these birds. Seabirds they have a very marked influence on the ecosystems where they form their colonies since, in addition to their function as predators, alongside with their depositions, they condition the primary producers and, consequently, the rest of the food chain. Their excrements contain large amounts of N, P and trace elements, most of which are bioavailable. In this study, besides bringing together the different works on nutrients and trace elements in excrements and differentiating some terms referring to these excrements, a brief historical overview of their importance for agriculture is made. In addition, the impacts produced by these birds on the ecosystem are also analysed according to two levels, at a global and local level. At each of these levels, a current state of the effects on the different compartments of the ecosystems is made, from the biota to the soils, the water or the atmosphere. This review supports the idea that more studies are needed both at the atmospheric level and in the terrestrial or marine environment for a better understanding of the changes these birds generate.

Gastrointestinal and respiratory exposure of water birds to endocrine disrupting phenolic compounds

Aquatic birds found at the top of the trophic chain are exposed to xenobiotics present both in food and inhaled air. The aim of this study was to indicate and assess the routes and levels of exposure of aquatic birds to bisphenol A (BPA), 4-tert-octylphenol (4-t-OP) and 4-nonylphenol (4-NP). The birds constituting the study material (Clangula hyemalis, Alca torda, Mergus merganser) originated from by-catches (winter 2014-2016) in the Southern Baltic. The studies show that the exposure of birds to phenol derivatives is determined by the specifics of a compound, the habitat area, trophic level and food consumed. BPA was characterized by the highest intestinal concentrations in all birds (6.6-1176.2 ng^.g^-1 dw). Higher concentrations of 4-t-OP were determined in the lungs of birds from the eastern part of the Southern Baltic (9.1-135.7 ng^.g^-1 dw) and in the intestines of birds from the western part (<0.5-191.4 ng^.g^-1 dw). In the case of 4-NP, higher concentrations were found in the intestines of carnivorous species (64.9-524.5 ng^.g^-1 dw), and the lungs of benthos-eating species (39.4-399.7 ng^.g^-1 dw). The intestines that were most burdened with 4-NP were those of birds from the highest trophic level. Correlations between the concentrations of phenol derivatives in the blood and the intestines and lungs indicated that birds are exposed to the penetration of phenol derivatives through the digestive and respiratory tracts. BPA and 4-NP were characterized by the highest concentrations in the intestines and lungs, whereas 4-t-OP in blood (3.2-39.2 ng^.cm^-3), which may indicate the largest endocrine potential of this compound in birds. Significant differences in phenol derivatives concentrations in the intestines and lungs of birds from the western and eastern part of the Southern Baltic, shows that these tissues can be useful for assessing the contamination of the environment with EDCs.

Mercury Exposure in Birds Linked to Marine Ecosystems in the Western Mediterranean

Mercury (Hg), particularly as methylmercury (MeHg), is a nonessential, persistent, and bioaccumulative toxic element with high biomagnification capacity and is considered a threat to marine environments. We evaluated total Hg concentrations in liver, kidney, and brain in 62 individuals of 9 bird species linked to marine ecosystems from western Mediterranean admitted in a Wildlife Rehabilitation Center (WRC) (Alicante, Spain, 2005-2020). Age- and sex-related differences in Hg levels, as well as the cause of admission to the WRC, were also evaluated in certain species. The species studied were: northern gannet (Morus bassanus), European shag (Phalacrocorax aristotelis), great cormorant (Phalacrocorax carbo), osprey (Pandion haliaetus), Balearic shearwater (Puffinus mauretanicus), yellow-legged gull (Larus michahellis), razorbill (Alca torda), common tern (Sterna hirundo), and black-headed gull (Chroicocephalus ridibundus). Concentrations in feathers of 27 individuals, and concentrations in internal tissues in 7 other individuals of 7 different species were also reported but not statistically evaluated due to the limited number of samples. Results suggest that individuals were chronically exposed to Hg through diet. The differences in Hg concentrations among species may be explained by their diet habits. Mercury concentrations strongly correlated between tissues (r = 0.78-0.94, p < 0.001, n = 61-62). Some individuals of certain species (i.e., European shag, northern gannet, and great cormorant) showed Hg concentrations close to or above those described in the literature as causing reproductive alterations in other avian species. Consequently, certain individuals inhabiting western Mediterranean could be at risk of suffering long-term, Hg-related effects. Some of the species evaluated are listed within different categories of threat according to the International Union for Conservation of Nature (IUCN) and are endangered at a national level, so this study will provide valuable information for assessors and authorities in charge of the management of the environment and pollution.

Toxic elements in blood of red-necked nightjars (Caprimulgus ruficollis) inhabiting differently polluted environments

Toxic metals have been widely reported in avian tissues due to their well-known accumulation capacity and adverse effects. However, rare earth elements (REE) and other minor elements (ME) are becoming a new threat due to their use in modern technology. Presently, exposure data are limited and no studies have been reported in wildlife. The order Caprimulgiformes is among the most understudied groups of birds lacking blood ecotoxicological data. One major constraint is the small blood sample volume that can be collected to ensure animal welfare, which limits analyses. In order to shed light on these collective issues, we sampled 48 red-necked nightjars (Caprimulgus ruficollis) inhabiting three different scenarios of contaminant exposure (agricultural-urban area, n = 15; mining area, n = 17; and control area, n = 16) in southeastern Spain, and report for the first time concentrations of 50 elements (i.e. trace elements, ATSDR's list toxic elements, REE and ME) using a recently developed technique able to analyze them by ICP-MS in very small volumes of blood (130 μL). Concentrations of As, Cd, Pb and Mn were significantly higher in individuals captured at the mining area compared to the other sites. Lead levels in the mine site were of particular concern since it was in the range of blood concentrations related to subclinical/clinical effects in other species, and in our study were associated with decreased hematocrit values (up to 44% hematocrit depression at blood concentrations >1000 ng/ml w.w.). Moreover, additive effects related to metal cocktail exposure in the mining area could be expected. Age and gender-related differences in blood concentrations were found for some elements. Even though most REE and ME concentrations were close to the LOQ, some of these emerging contaminants may trigger sublethal effects that, together with the ATSDR's list toxic elements, need to be carefully evaluated in a future study.

Mercury and Organochlorine Pesticides in Tissues of Loggerhead Sea Turtles (Caretta caretta) Stranded Along the Southwestern Mediterranean Coastline (Andalusia, Spain)

Nineteen loggerhead sea turtles (Caretta caretta) stranded along the southwestern Mediterranean coastline (Andalusia) were used in this study. A total of 68 samples of fat (n = 18), liver (n = 15), kidney (n = 13), pectoral muscle (n = 19), and brain (n = 3) were analysed for total mercury (Hg) and organochlorine pesticides [OC: ∑Dichlorodiphenyltrichloroethanes (∑DDT), ∑Hexachlorocyclohexane (∑HCH), ∑Heptachlor, ∑Drins and ∑Endosulfan]. These loggerhead sea turtles showed tissue Hg and OC concentrations similar to or lower than those reported in other studies. Few growth-related variations in Hg or OC levels in relation to straight carapace length were found, probably because the specimens were mostly juveniles. This study will help to fill the gap on spatio-temporal exposure data and ascertain the real world-wide picture of the contamination levels in loggerhead sea turtles.

Tools for non-invasive sampling of metal accumulation and its effects in Mediterranean pond turtle populations inhabiting mining areas

Among reptiles, freshwater turtle species have high potential for metal accumulation because of their long lifespan or their aquatic and terrestrial habits. In order to monitor metal bioaccumulation, determine potential toxic effects, and investigate tools for non-invasive metal sampling in reptiles, we studied lead (Pb) and mercury (Hg) accumulation in Mediterranean pond turtles (Mauremys leprosa) inhabiting two former mining areas, one of them with high environmental concentrations of Pb (Sierra Madrona-Alcudia Valley district) and the other one with high environmental concentrations of Hg (Almadén district). Individuals from the Pb mining area showed mean blood concentrations (i.e. 5.59 μg Pb/g dry weight, d.w.) that were higher than those measured in other populations. Blood Hg concentrations were highest (8.83 μg Hg/g d.w.) in the site close to the former Hg mines, whereas blood Hg concentrations in terrapins from another site of Almadén district, located ∼28 km downstream, were not different from locations at the non-mining area. Animals from the Pb-contaminated site showed evidence of oxidative stress, whereas those from the Hg-contaminated site showed increased activity of the antioxidant enzyme glutathione peroxidase, as well as reduced circulating levels of the main endogenous antioxidant peptide, glutathione. Concentrations measured in feces and carapace scutes were useful indicators to monitor blood concentrations of Pb, but not of Hg. Our results provide evidence of the usefulness of freshwater turtles as sentinels of chronic metal pollution, and validate non-invasive tools to advance Pb monitoring in reptiles.

From Mexico to the Beagle Channel: A review of metal and metalloid pollution studies on wildlife species in Latin America

Emissions of metals and metalloids (Hg; Cd; Cr; Cu; Pb; Ni; Zn; Fe; Mn; As; Se) generated by natural (e.g., geothermal activity) or anthropic causes (eg., industry or mining) represent a worldwide contamination problem, especially in developing countries. Exposure to high concentrations of these elements is harmful to living beings, including humans. Information on this type of contamination is scarce and fragmented, limiting research which could benefit from these data. To know the state of the research, we reviewed the studies of environmental pollution by metals and metalloids carried out on animal species in Latin America. The use of animals as biomonitors of contamination by metals and metalloids is a continuously expanding practice that allows for early detection of problems. With this work, we were able to identify the most studied areas in Latin America (Amazon, Gulf of California, coastal area between Rio de Janeiro and Florianopolis and River Plate Estuary). Moreover, we provide information on the most studied metals (Hg, Cd, Cu, Pb, Zn) and wild species, which evidence the use of endangered species. The data reviewed should help researchers to direct their efforts towards sparsely researched areas and facilitate bibliographic consultation of scientific information on exposure to metals and metalloids in Latin America.

Metal content in the liver, kidney, and feathers of Northern gannets, Morus bassanus, sampled on the Spanish coast

The value of birds as bioindicators for monitoring the environmental inorganic elements has been globally recognized. In this context, due to its well-known ecology and population stability, the Northern gannet (Morus bassanus) could be particularly useful. Dead Northern gannets (n = 30) were collected and samples from the liver, kidney, and feathers were taken, dried, mineralized, and finally analyzed via ICP-MS. Metals and metalloids, namely As, Cd, Hg, Pb, and Zn, associated with environmental pollution and toxicity on living organisms, were evaluated. The mean highest concentrations of As, Hg, and Zn were found in the liver (0.916, 7.026, and 89.81 mg/kg dry weight, respectively). For Cd, the kidney showed the highest mean concentration (17.51 mg/kg dry weight), whereas for Pb, this value corresponded to the feathers (0.399 mg/kg dry weight). Significant differences were found between the age classes in terms of contaminant concentrations, with the adults exhibiting higher metal levels. This difference was significantly relevant for Pb and Hg, where the effect of age was observed for all the considered tissues. When considering the effect of gender, no significant differences were observed, in agreement with similar studies performed in other geographical regions. Finally, positive correlations between the concentrations of Hg and Pb in the feathers and in the liver (r = 0.688, p < 0.001 and r = 0.566, p < 0.001, respectively) were observed, as well as between the feather and kidney concentrations (r = 0.685, p < 0.001) indicating the possibility to use feathers, a non-invasive biomonitoring tissue, for better understanding Hg and Pb exposure in seabirds.

Methylmercury and total mercury content in soft tissues of two bird species wintering in the Baltic Sea near Gdansk, Poland

Of the various forms of Hg occurring in nature, (mono) methylmercury (MeHg) is an especially toxic form and practically all forms of Hg can be converted into MeHg as a result of natural processes. Total mercury (THg) and MeHg were determined in tissues of two piscivorous birds: razorbill Alca torda and black-throated loon Gavia arctica to provide baseline data on current mercury concentrations for liver, kidneys and pectoral muscle mercury concentrations of birds which winter on the south Baltic Sea coast. Intra and inter-specific comparisons were carried out. The study is conducted between winter and autumn and the distributions of mercury in tissues were compared with data in other studies. The following paper contains discussion of the results based on the statistical analysis and ecology aspect. The highest average Hg content was in the liver (loon ≈ 3.86 mg kg^-1 dw; razorbill ≈ 1.57 mg kg^-1 dw), then in the kidneys (loon ≈ 3.14 mg kg^-1 dw; razorbill ≈ 1.53 mg kg^-1 dw) and the lowest concentrations were in pectoral muscles (loon ≈ 1.97 mg kg^-1 dw; razorbill ≈ 0.67 mg kg^-1 dw).

Enrichment of trace elements in colonies of the yellow-legged gull (Larus michahellis) in the Atlantic Islands National Park (Galicia-NW Spain)

Marine-derived nutrients are known accumulate in seabird breeding colonies due to the deposition of nutrient-rich biological materials, thus greatly altering the functioning and dynamics of these terrestrial ecosystems. Here we present the results of a sampling survey carried out during three years in yellow-legged gull colonies in the Atlantic Islands of Galicia National Park (NW Spain) with the aim of evaluating the influence of the colonies on the accumulation of trace elements, including micronutrients (Cu, Zn, Se, Co, Mo, Ni) and toxic elements (Cr, Cd, Hg, Pb, As, Ag), in the surrounding environments. For this purpose, we analysed samples of biological materials produced by the seabirds (pellets, excrement, feathers, eggs) and of soil, plants and inland water from several different subcolonies and control zones without seabirds. The concentrations of most of the elements were higher in excrement and pellets (mean values: Zn: 152, As: 50 mg kg^-1, Cd: 6, Co: 5 mg kg^-1) than in feathers and eggs. The flow of trace elements into the breeding colonies, considering only the excrement, revealed a very high level of trace element deposition for a supposedly pristine environment (Zn: 2667, Cd: 70, Cu: 315, As: 64 g ha^-1). The total concentrations of trace elements in soil were consistent with the long-term impact of the seabirds. Thus, the values in areas which this impact was greatest were significantly higher than in the control zones, particularly considering the most labile geochemical fractions of the soil. The concentrations of some elements (i.e. Co, As, Cd) were also higher in the inland waters in the colonies than in control zones. Finally, the concentration of trace elements in plants varied depending on the species and element considered.

Mercury concentrations in blood, brain and muscle tissues of coastal and pelagic birds from northeastern Canada

Mercury (Hg) is a toxic element which has increased in marine environments for more than a century, due largely to anthropogenic activities, and biomagnifies in food chains to harmful levels in some top predators like waterfowl and seabirds. We analysed total mercury (THg) concentrations in blood, brain and muscle tissue from healthy specimens of 13 coastal and pelagic bird species from eastern and northern Canada to provide a baseline on current concentrations, especially for brain concentrations which are highly underrepresented in the literature. We also examined within and among tissues relationships of THg concentrations within individuals. THg concentrations were generally higher in pelagic species and scavenging gulls, when compared to coastal waterfowl. Brain and muscle tissue had similar concentrations of THg in the birds examined, but both of these tissues had lower concentrations that those found in blood. Our results, and that of a previous study, suggest that body condition has a large influence on blood THg concentrations and should be considered when using blood as a sampling medium. Many of the species we examined had tissue THg above levels known to cause deleterious, sublethal effects in some species.

Trace elements in biomaterials and soils from a Yellow-legged gull (Larus michahellis) colony in the Atlantic Islands of Galicia National Park (NW Spain)

Seabird colonies drastically transform the sites that they inhabit. Although the influence of seabirds on nutrient cycling has been investigated in numerous studies, the effects on trace elements has scarcely been considered. In this study, we determined the total contents of 9 trace elements in biomaterials (excrement, pellets, feathers and eggs) and soils in relation to the presence the Yellow-legged gull Larus michahellis. The concentrations of Zn, Cu and As were particularly high in the pellets and excrement. The total contents of the trace elements were significantly higher in the soils in the sub-colonies in which Yellow-legged gulls predominate than in soil from the control zone (with no gulls). The difference was even higher for the most reactive geochemical fractions. We observed that the oxidizable fraction was the most relevant fraction for almost all trace elements, indicating the importance of organic matter in trace element retention in sandy soils.

Mercury in the feathers of bird scavengers from two areas of Patagonia (Argentina) under the influence of different anthropogenic activities: a preliminary study

Mercury (Hg) is a global pollutant that bioaccumulates and biomagnifies in food chains and is associated with adverse effects in both humans and wildlife. We used feather samples from bird scavengers to evaluate Hg concentrations in two different areas of Northern Patagonia. Hg concentrations were analyzed in feathers obtained from turkey vultures (Cathartes aura), Black Vultures (Coragyps atratus), and southern crested caracaras (Caracara plancus) from the two areas of Northern Patagonia (Argentina): Bariloche and El Valle. Hg was detected in all the samples analyzed, but the concentrations can be considered low for the three species in both sampling areas. The mean concentration of Hg in Bariloche was 0.22 ± 0.16 mg/kg dry weight (d.w.) in black vulture, 0.13 ± 0.06 mg/kg d.w. in turkey vulture, and 0.13 ± 0.09 mg/kg d.w. in southern crested caracara; in El Valle, the mean concentration of Hg was 1.02 ± 0.89 mg/kg d.w. in black vulture, 0.53 ± 0.82 mg/kg d.w. in turkey vulture, and 0.54 ± 0.74 mg/kg d.w. in southern crested caracara. Hg concentrations in feathers were explained by the sampling area but not by the species. The concentrations of Hg contamination were comparable to those obtained in other studies of terrestrial raptors and aquatic bioindicator raptors. The species of the present study occur throughout much of North and South America. Thus, they may be appropriate bioindicators across the species' range, which is particularly useful as a surrogate, especially in distribution areas shared with endangered scavengers such as the California condor (Gymnopsys californianus) and the Andean Condor (Vultur gryphus).

Per- and polyfluoroalkyl substances in plasma and feathers of nestling birds of prey from northern Norway

Plasma samples from nestlings of two top predators, White-tailed eagle (Haliaeetus albicilla) and Northern goshawk (Accipiter gentilis) from northern Norway were analysed for a wide range of per- and polyfluoroalkyl substances (PFASs). Body feathers from the White-tailed eagles were also analysed and significant associations between specific PFASs in blood plasma and body feathers were found (0.36 <R² < 0.67; all p < 0.05). This result suggests that analysing body feathers of White-tailed eagle could potentially be a useful non-invasive strategy to monitor PFASs exposure in nestlings of this species. White-tailed eagles showed significantly higher levels of contaminants than Northern goshawks (plasma ∑PFASs Median = 45.83 vs 17.02ngmL^-1, p <0.05). The different exposure between both species seemed to be related to different dietary input, as quantified by stable carbon and nitrogen isotope analysis of body feathers. A priori, the bird of prey populations studied are not at risk for PFASs, since the levels in plasma of both species were hundreds to thousand times lower than the toxic reference values reported for predatory birds. However, further studies on larger sample sizes are needed to confirm this hypothesis since toxic thresholds for nestling birds of prey are not established.

Assessment of mercury exposure and maternal-foetal transfer in Miniopterus schreibersii (Chiroptera: Miniopteridae) from southeastern Iberian Peninsula

Mercury (Hg) is a highly toxic and widely distributed metal that is bioaccumulated in insectivorous mammals and may cause adverse effects on the reproductive system. Bats are considered excellent Hg bioindicators due to their wide distribution, life span, trophic position, metabolic rate and food intake. However, few studies have analysed Hg residues in bats, and to the best of our knowledge, no studies have been made in the Iberian Peninsula. The main aim of this study was to undertake the first ever assessment of Hg exposure in Schreiber's bent-winged bats inhabiting a natural cave in the southeast of Spain. The findings suggest that Schreiber's bent-winged bats in the sampling area are chronically exposed to low levels of Hg. The Hg concentrations found in different tissues (fur, kidney, liver, muscle and brain) were below the threshold levels associated with toxic effects in mammals. Non-gestating females showed Hg concentrations in the brain and muscle that doubled those found in gestating females. This could be due to Hg mobilization from the mother to the foetus in gestating females, although other factors could contribute to explain this result such as variations in hunting areas and the insect-prey consumed and/or different energetic needs and average food consumption during the breeding season. Hg levels were 1.7 times higher, although not significant, in foetus' brains than in the maternal brains, and Hg concentration in foetus' brain was significantly correlated with levels in the corresponding mothers' kidney. These results suggest that there could be an active mother-to-foetus transfer of Hg in bats, which would be of special relevance in a scenario of higher Hg exposure than that found in this study. However, further research is needed to support this view due to the limited number of samples analysed. Given the scarce ecotoxicological data available for bats and their protected status, we encourage further opportunistic studies using carcasses found in the field, the validation of non-destructive samples such as fur and guano for Hg monitoring, and new modelling approaches that will increase the data needed for proper ecological risk assessment in bat populations.

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.

Interspecific differences in the antioxidant capacity of two Laridae species exposed to metals

The main aim of the present study was to assess the concentration of metals (Pb, Cd, Hg, Cu and Zn) in blood, and elucidate their potential effects on oxidative stress biomarkers in red blood cells of Audouin's gull (Ichthyaetus audouinii) and Slender-billed gull (Chroicocephalus genei) chicks in Southeastern Spain. For this purpose, total glutathione (GSH) content, antioxidant enzymes activities (glutathione peroxidase, GPx; superoxide dismutase, SOD; catalase, CAT and glutathione-S-transferase, GST), and lipid peroxidation (TBARS) were analyzed. In general, metal exposure in both species can be considered low, except for Hg in Audouin's gull. Our findings show higher antioxidant levels in Audouin's gull than in Slender-billed gull; probably due to a combination of different basal antioxidant capacity between species, and to an up-regulation of the antioxidant system in Audouin's gull as a response to the higher Hg, Cu and Zn concentrations. This could reduce the production of TBARS keeping them at lower levels than those found in Slender-billed gull. In spite of this, the significantly higher Hg levels found in Audouin's gull (13.6µg/dl wet weight) in comparison to Slender-billed gull (2.7µg/dl), likely related to their different diet and the former consuming discarded fish, were able to produce lipid peroxidation in this species. The positive effect of Hg on SOD activity in Slender-billed gull, and of Pb on GSH levels in Audouin's gull, could reflect the necessity of the organism to upregulate these antioxidants to balance the increased oxidative stress caused by metals. The degree of metal exposure seems to be essential in the response of the antioxidant system, which may suffer up or down-regulations depending on metal concentrations. This study supports the interactive effects of metals on oxidative stress biomarkers, the complexity of the antioxidant system and the close cooperation between antioxidants, which requires the study of several metals and biomarkers to evaluate oxidative stress and damage in wild birds.

Mercury in wintering seabirds, an aggravating factor to winter wrecks?

Every year, thousands of seabirds are cast ashore and are found dead along the coasts of North America and Western Europe. These massive mortality events called 'winter wrecks' have generally been attributed to harsh climatic conditions and prolonged storms which affect bird energy balance and impact their body condition. Nevertheless, additional stress factors, such as contaminant body burden, could potentially cumulate to energy constraints and actively contribute to winter wrecks. However, the role played by these additional factors in seabird massive winter mortality has received little attention to date. In February/March 2014, an unprecedented seabird wreck occurred along the Atlantic French coasts during which > 43,000 seabirds were found dead. By analyzing mercury (Hg) concentrations in various tissues collected on stranded birds, we tested the hypothesis that Hg played a significant role in this mortality. More specifically, we aimed to (1) describe Hg contamination in wintering seabirds found along the French coasts in 2014, and (2) determine if Hg concentrations measured in some vital organs such as kidney and brain reached toxicity thresholds that could have led to deleterious effects and to an enhanced mortality. We found some of the highest Hg levels ever reported in Atlantic puffins, common guillemots, razorbills and kittiwakes. Measured concentrations ranged from 0.8 to 3.6 μg · g(-1) of dry weight in brain, 1.3 to 7.2 μg · g(-1) in muscle, 2.5 to 13.5 μg · g(-1) in kidney, 2.9 to 18.6 μg · g(-1) in blood and from 3.1 to 19.5 μg · g(-1) in liver. Hg concentrations in liver and brain were generally below the estimated acute toxicity levels. However, kidney concentrations were not different than those measured in the liver, and above levels associated to renal sub-lethal effects, suggesting a potential Hg poisoning. We concluded that although Hg was not directly responsible for the high observed mortality, it has been a major aggravating stress factor for emaciated birds already on the edge. Importantly, this study also demonstrated that total blood, which can be non-lethally collected in seabirds, can be used as a predictor of Hg contamination in other tissues.

Decline in an Atlantic Puffin Population: Evaluation of Magnitude and Mechanisms

Determining which demographic and ecological parameters contribute to variation in population growth rate is crucial to understanding the dynamics of declining populations. This study aimed to evaluate the magnitude and mechanisms of an apparent major decline in an Atlantic Puffin Fratercula arctica population. This was achieved using a 27-year dataset to estimate changes in population size and in two key demographic rates: adult survival and breeding success. Estimated demographic variation was then related to two ecological factors hypothesised to be key drivers of demographic change, namely the abundance of the main predator at the study site, the Great Skua Stercorarius skua, and Atlantic Puffin chick food supply, over the same 27-year period. Using a population model, we assessed whether estimated variation in adult survival and reproductive success was sufficient to explain the population change observed. Estimates of Atlantic Puffin population size decreased considerably during the study period, approximately halving, whereas Great Skua population estimates increased, approximately trebling. Estimated adult Atlantic Puffin survival remained high across all years and did not vary with Great Skua abundance; however, Atlantic Puffin breeding success and quantities of fish prey brought ashore by adults both decreased substantially through the period. A population model combining best possible demographic parameter estimates predicted rapid population growth, at odds with the long-term decrease observed. To simulate the observed decrease, population models had to incorporate low immature survival, high immature emigration, or increasingly high adult non-breeding rates. We concluded that reduced recruitment of immatures into the breeding population was the most likely cause of population decrease. This study showed that increase in the size of a predator population does not always impact on the survival of adult prey and that reduced recruitment can be a crucial determinant of seabird population size but can easily go undetected.

A review on exposure and effects of arsenic in passerine birds

Arsenic (As) is a metalloid of high concern because of its toxic effects for plants and animals. However, it is hard to find information on this metalloid in passerines. This review presents a comprehensive overview of As exposure and effects in birds, and more particularly in passerines, as a result of an extensive search of the literature available. Internal tissues are the most frequently analyzed matrices for As determination in passerines (37.5% of the reviewed studies used internal tissues), followed by feathers and eggs (32.5% each), feces (27.5%), and finally blood (15%). A clear tendency is found in recent years to the use of non-destructive samples. Most studies on As concentrations in passerines have been done in great tit (Parus major; 50%), followed by pied flycatcher (Ficedula hypoleuca; 22.5%). Some factors such as diet and migratory status are crucial on the interspecific differences in As exposure. More studies are needed to elucidate if intraspecific factors like age or gender affect As concentrations in different tissues. The literature review shows that studies on As concentrations in passerines have been done mainly in the United States (30%), followed by Belgium (22.5%), and Finland (20%), making evident the scarce or even lack of information in some countries, so we recommend further research in order to overcome the data gap, particularly in the southern hemisphere. Studies on humans, laboratory animals and birds have found a wide range of effects on different organ systems when they are exposed to different forms of As. This review shows that few field studies on As exposure and effects in passerines have been done, and all of them are correlative so far. Arsenic manipulation experiments on passerines are recommended to explore the adverse effects of As in free-living populations at similar levels to those occurring in the environment.

CAPSULE

This review summarizes the most interesting published studies on As exposure and effects in passerines.

An overview of existing raptor contaminant monitoring activities in Europe

Biomonitoring using raptors as sentinels can provide early warning of the potential impacts of contaminants on humans and the environment and also a means of tracking the success of associated mitigation measures. Examples include detection of heavy metal-induced immune system impairment, PCB-induced altered reproductive impacts, and toxicity associated with lead in shot game. Authorisation of such releases and implementation of mitigation is now increasingly delivered through EU-wide directives but there is little established pan-European monitoring to quantify outcomes. We investigated the potential for EU-wide coordinated contaminant monitoring using raptors as sentinels. We did this using a questionnaire to ascertain the current scale of national activity across 44 European countries. According to this survey, there have been 52 different contaminant monitoring schemes with raptors over the last 50years. There were active schemes in 15 (predominantly western European) countries and 23 schemes have been running for >20years; most monitoring was conducted for >5years. Legacy persistent organic compounds (specifically organochlorine insecticides and PCBs), and metals/metalloids were monitored in most of the 15 countries. Fungicides, flame retardants and anticoagulant rodenticides were also relatively frequently monitored (each in at least 6 countries). Common buzzard (Buteo buteo), common kestrel (Falco tinnunculus), golden eagle (Aquila chrysaetos), white-tailed sea eagle (Haliaeetus albicilla), peregrine falcon (Falco peregrinus), tawny owl (Strix aluco) and barn owl (Tyto alba) were most commonly monitored (each in 6-10 countries). Feathers and eggs were most widely analysed although many schemes also analysed body tissues. Our study reveals an existing capability across multiple European countries for contaminant monitoring using raptors. However, coordination between existing schemes and expansion of monitoring into Eastern Europe is needed. This would enable assessment of the appropriateness of the EU-regulation of substances that are hazardous to humans and the environment, the effectiveness of EU level mitigation policies, and identify pan-European spatial and temporal trends in current and emerging contaminants of concern.

Effects of heavy metals on biomarkers for oxidative stress in Griffon vulture (Gyps fulvus)

Metals are involved in the formation of reactive oxygen species (ROS) which may result in metal-related oxidative stress that can lead to oxidative damage to lipids, DNA and proteins. It is necessary to understand the mechanisms of metal toxicity in wild birds, and the concentrations that cause effects on oxidative stress biomarkers. The aim of this study is to assess the concentrations of lead (Pb), cadmium (Cd), mercury (Hg), copper (Cu) and zinc (Zn) with regards to oxidative stress in blood samples of 66 Griffon vultures (Gyps fulvus) from two areas of the Autonomous Community of Valencia (East of Spain). The two study areas (Alcoy n=36 and Cinctorres n=30) were selected as random locations of interest that had not yet been studied, and are feeding stations where supplementary food, mainly of pork origin, is provided for vultures. Given that the two study areas are not considered polluted sites, we expected to find low metal concentrations. However, there are no known threshold concentrations at which metals can affect antioxidant systems, and low metal levels may have an effect on antioxidant biomolecules. In this study, since sampling was done at the beginning of the hunting season, the low Pb levels found in most Griffon vultures from Alcoy and Cinctorres (median=12.37 and 16.26μg/dl, respectively) are suggestive of background levels usually found in vultures that feed on pork carcasses all year round. The ingestion of game meat with bullet fragments in carcasses or with Pb shots embedded in the flesh could be the cause of the high blood Pb concentrations found in three vultures from Cinctorres (83, 290 and 362μg/dl). Griffon vultures feeding in Cinctorres had enhanced CAT and GST activities and tGSH concentrations, which may be interpreted as protective response against the higher TBARS levels. This study provides threshold concentrations at which metals affect antioxidant system derived from 66 samples of Griffon vulture. Blood Cd concentrations greater than 0.05μg/dl produced an induction of 33% in GPx and of 44% in CAT activity in erythrocytes of vultures from Alcoy. Hg concentrations in blood higher than 3μg/dl produced an induction of 10% in SOD activity. Concentrations of Pb above 15µg/dl in blood produced an inhibition of 12.5% in GPx and 11.3% in CAT activity, and a TBARS induction of 10.7% in erythrocytes of Griffon vultures.

Factors that influence mercury concentrations in nestling Eagle Owls (Bubo bubo)

Mercury (Hg) is a global pollutant that bioaccumulates and biomagnifies in food chains, and is associated with adverse effects in both humans and wildlife. The Hg levels detected in blood obtained from Eagle Owl (Bubo bubo) chicks in Southeast Spain (Murcia) can be considered low (mean Hg concentration in blood from 2006 to 2012 was 36.83 ± 145.58 μg/l wet weigh, n=600), and it is therefore unlikely that Hg pollution can negatively affect their breeding. Positive correlation (r=0.339, p<0.001, n=229) was found to exist between the Hg concentrations in the blood and back feathers of the chicks. We provide a regression equation that could be helpful to estimate blood Hg levels when analyzing Hg concentrations in back feathers. Blood Hg concentrations in Eagle Owls have shown positive correlations with Hg levels in rabbit muscles, more evident in nests from the Northern area (r=0.600, p=0.014, n=16), where rabbits are the main prey of Eagle Owls. The best Linear Mixed Model to explain variations in blood Hg concentrations in nestling Eagle Owls includes year and location within the mining area as variables. The variable year is assigned the largest value of relative importance, followed by the location in the ancient mining sites and then the zone. Rainfalls may have an effect on the temporal differences in the blood Hg concentrations of nestling Eagle Owls. Although the studied region is not considered Hg polluted, the Hg levels were higher in Eagle Owls and European Rabbits from areas within the ancient mining sites as compared to those in the entire region. This result shows that spatial differences in Hg concentrations in Eagle Owls may be affected by local contamination, and that the role of diet composition may be less significant.