Running the gauntlet; flyway-wide patterns of pollutant exposure in blood of migratory shorebirds.

Shorebirds (order Charadriiformes) are among the world's most threatened avian taxa. Within the East Asian-Australasian Flyway (EAAF), a major threat to shorebirds' survival may be the gauntlet of pollution along the flyway. Metals, persistent organic pollutants (POPs), and per-/polyfluoroalkyl substances (PFASs) persist in the environment to the detriment of wildlife. In this study, we analysed element and PFAS concentrations in blood from 142 individuals across six species of Arctic-breeding migratory shorebirds with contrasting population trends, to discern species- and site-specific pollution differences, and determine how pollution correlated with population trends of EAAF shorebirds. Potential within-year pollution variations were investigated by blood-sampling birds at two sites, representing different points in the birds' annual migrations: staging in Taiwan on southward migrations and at non-breeding grounds in Western Australia (WA). Species' pollutant concentrations were compared to established population trends. Concentrations of potentially toxic elements were low in most individuals regardless of species. PFASs (range: <0.001-141 ng/g), Hg (<0.001-9910 ng/g) and Pb (<0.01-1210 ng/g) were higher in Taiwan than in WA (PFAS Taiwan median: 14.5 ng/g, WA median: 3.45 ng/g; Hg Taiwan: 338 ng/g, WA: 23.4 ng/g; Pb Taiwan: 36.8 ng/g, WA: 2.26 ng/g). Meanwhile As (range <0.001-8840 ng/g) and Se (290-47600 ng/g) were higher in WA than Taiwan (As Taiwan median: 500 ng/g, WA median: 1660 ng/g; Se Taiwan: 5490 ng/g, Se WA: 23700 ng/g). Nevertheless, pollutant concentrations in a subset of individuals may exceed sublethal effect thresholds (As, Se and PFASs). Finally, we found no consistent differences in pollution among species and demonstrated no correlation between pollution and population trends, suggesting pollution is likely not a major driver for population declines of EAAF shorebirds. However, ongoing and locally heavy environmental degradation and exposure to other contaminants not investigated here, such as POPs, warrants continued consideration when managing EAAF shorebird populations.

Mercury exposure and trophic ecology of urban nesting black-legged kittiwakes from France.

Seabirds are increasingly used as bioindicators for assessing the chemical contamination of marine ecosystems, including by mercury (Hg) worldwide. However, some geographical areas are still poorly documented, as metropolitan France that is home to 28 seabird species including the black-legged kittiwake Rissa tridactyla, in the part of the southern limit of the North Atlantic range of the species. Here, we investigated Hg contamination and trophic ecology of black-legged kittiwakes breeding in the harbour of Boulogne-sur-Mer, Northern France. Mean blood Hg concentration was 4.81 ± 1.20 µg g-1 dw (dry weight), 3.66 ± 0.75 µg g-1 dw and 0.43 ± 0.07 µg g-1 dw for adult males, adult females, and chicks, respectively. According to Hg toxicity benchmarks for avian blood, 30% of the sampled adults were considered to be at moderate risk to Hg toxicity. Stable isotope and food analyses showed that highest δ15N values (reflecting a higher trophic position) were related to highest blood Hg concentrations in adult birds, and that Atlantic herring (Clupea harengus) and Atlantic mackerel (Scomber scombrus) were the main prey. Adult kittiwakes from Boulogne-sur-Mer showed Hg levels three times higher than those found in Arctic nesting kittiwakes, where sublethal effects have been documented. This study provides a first description of Hg contamination of black-legged kittiwakes breeding in France and calls for future ecotoxicological research to assess the vulnerability of this species in the southern part of its distribution range.

Pilot study on neonicotinoids in Finnish waterbirds: no detectable concentrations in common goldeneye (Bucephala clangula) plasma.

Neonicotinoids have been detected in farmland-associated birds and exposure to these insecticides has been linked to adverse effects. Even though neonicotinoids are mobile and persistent and have been detected in surface waters and aquatic invertebrates, there is a considerable lack of knowledge on their occurrence in waterbirds. Here we investigated the occurrence of seven neonicotinoids and some of their transformation products (imidacloprid, thiacloprid, thiamethoxam, acetamiprid, clothianidin, dinotefuran, nitenpyram, 6-chloronicotinic acid, hydroxy-imidacloprid, imidacloprid-urea, imidacloprid-olefin, thiamethoxam-urea, thiacloprid-amide, acetamiprid-acetate, and acetamiprid-desmethyl) in blood plasma of 51 incubating female common goldeneyes (Bucephala clangula). We collected samples from five different regions from southern to northern Finland encompassing rural and urban settings in coastal and inland areas. Surprisingly, none of the targeted neonicotinoids was found above the limit of detection in any of the samples. As neonicotinoid concentrations in wild birds can be very low, a likely reason for the nil results is that the LODs were too high; this and other possible reasons for the lack of detection of neonicotinoids in the goldeneyes are discussed. Our results suggest that neonicotinoid exposure in their breeding areas is currently not of major concern to female goldeneyes in Finland. Even though this study did not find any immediate danger of neonicotinoids to goldeneyes, further studies including surface water, aquatic invertebrates, and other bird species could elucidate potential indirect food chain effects.

Mercury contamination and potential health risk to French seabirds: A multi-species and multi-site study.

Mercury (Hg) is a naturally occurring highly toxic element which circulation in ecosystems has been intensified by human activities. Hg is widely distributed, and marine environments act as its main final sink. Seabirds are relevant bioindicators of marine pollution and chicks are particularly suitable for biomonitoring pollutants as they reflect contamination at short spatiotemporal scales. This study aims to quantify blood Hg contamination and identify its drivers (trophic ecology inferred from stable isotopes of carbon (δ13C) and nitrogen (δ15N), geographical location, chick age and species) in chicks of eight seabird species from 32 French sites representing four marine subregions: the English Channel and the North Sea, the Celtic Sea, the Bay of Biscay and the Western Mediterranean. Hg concentrations in blood ranged from 0.04 µg g-1 dry weight (dw) in herring gulls to 6.15 µg g-1 dw in great black-backed gulls. Trophic position (δ15N values) was the main driver of interspecific differences, with species at higher trophic positions showing higher Hg concentrations. Feeding habitat (δ13C values) also contributed to variation in Hg contamination, with higher concentrations in generalist species relying on pelagic habitats. Conversely, colony location was a weak contributor, suggesting a relatively uniform Hg contamination along the French coastline. Most seabirds exhibited low Hg concentrations, with 74% of individuals categorized as no risk, and < 0.5% at moderate risk, according to toxicity thresholds. However, recent work has shown physiological and fitness impairments in seabirds bearing Hg burdens considered to be safe, calling for precautional use of toxicity thresholds, and for studies that evaluate the impact of Hg on chick development.

Assessment of contaminants, health and survival of migratory shorebirds in natural versus artificial wetlands - The potential of wastewater treatment plants as alternative habitats.

The rapid destruction of natural wetland habitats over past decades has been partially offset by an increase in artificial wetlands. However, these also include wastewater treatment plants, which may pose a pollution risk to the wildlife using them. We studied two long-distance Arctic-breeding migratory shorebird species, curlew sandpiper (Calidris ferruginea, n = 69) and red-necked stint (Calidris ruficollis, n = 103), while on their Australian non-breeding grounds using an artificial wetland at a wastewater treatment plant (WTP) and a natural coastal wetland. We compared pollutant exposure (elements and per- and poly-fluoroalkyl substances/PFASs), disease (avian influenza), physiological status (oxidative stress) of the birds at the two locations from 2011 to 2020, and population survival from 1978 to 2019. Our results indicated no significant differences in blood pellet pollutant concentrations between the habitats except mercury (WTP median: 224 ng/g, range: 19-873 ng/g; natural wetland: 160 ng/g, 22-998 ng/g) and PFASs (total PFASs WTP median: 85.1 ng/g, range: <0.01-836 ng/g; natural wetland: 8.02 ng/g, <0.01-85.3 ng/g) which were higher at the WTP, and selenium which was lower at the WTP (WTP median: 5000 ng/g, range: 1950-34,400 ng/g; natural wetland: 19,200 ng/g, 4130-65,200 ng/g). We also measured higher blood o,o'-dityrosine (an indicator of protein damage) at the WTP. No significant differences were found for adult survival, but survival of immature birds at the WTP appeared to be lower which could be due to higher dispersal to other wetlands. Interestingly, we found active avian influenza infections were higher in the natural habitat, while seropositivity was higher in the WTP, seemingly not directly related to pollutant exposure. Overall, we found limited differences in pollutant exposure, health and survival of the shorebirds in the two habitats. Our findings suggest that appropriately managed wastewater treatment wetlands could provide a suitable alternative habitat to these migratory species, which may aid in curbing the decline of shorebird populations from widespread habitat loss.