The use of blood in Anas clypeata as an efficient and non-lethal method for the biomonitoring of mercury

Mercury and methylmercury concentration in the feathers of two species of Kingfishers Megaceryle torquata and Chloroceryle amazona in the Upper Paraguay Basin and Amazon Basin

Mercury (Hg) contamination remains a significant environmental concern. In aquatic ecosystems, Hg can undergo methylation, forming its organic form, methylmercury (MeHg), which bioaccumulates and biomagnifies in the food chain, ultimately reaching the top predators, including waterfowl. The objective of this study was to investigate the distribution and levels of Hg in wing feathers, with a specific focus on evaluating heterogeneity in the primary feathers of two kingfisher species (Megaceryle torquata and Chloroceryle amazona). The concentrations of total Hg (THg) in the primary feathers of C. amazona individuals from the Juruena, Teles Pires, and Paraguay rivers were 4.724 ± 1.600, 4.003 ± 1.532, and 2.800 ± 1.475 µg/kg, respectively. The THg concentrations in the secondary feathers were 4.624 ± 1.718, 3.531 ± 1.361, and 2.779 ± 1.699 µg/kg, respectively. For M. torquata, the THg concentrations in the primary feathers from the Juruena, Teles Pires, and Paraguay rivers were 7.937 ± 3.830, 6.081 ± 2.598, and 4.697 ± 2.585 µg/kg, respectively. The THg concentrations in the secondary feathers were 7.891 ± 3.869, 5.124 ± 2.420, and 4.201 ± 2.176 µg/kg, respectively. The percentage of MeHg in the samples increased during THg recovery, with an average of 95% in primary feathers and 80% in secondary feathers. It is crucial to comprehend the current Hg concentrations in Neotropical birds to mitigate potential toxic effects on these species. Exposure to Hg can lead to reduced reproductive rates and behavioral changes, such as motor incoordination and impaired flight ability, ultimately resulting in population decline among bird populations.

New insights on the use of bill sheath as a biomonitoring tool for mercury in two kingfisher species: A comparison with different tissues

Bird species have been widely used as suitable bioindicators of environmental mercury (Hg). However, there is still some debate about the most suitable tissue to indicate Hg body burden in birds. For a long time, blood and feathers have proved to be relevant to monitor Hg at different time scales, and recently, bill sheath has been suggested as a potential tissue to this end. In the present study, we evaluated THg in muscle, liver, feathers, claws, and bill sheath in two waterbird species (i.e. the ringed and the Amazon kingfishers) from the Teles Pires, Juruena and Paraguay rivers. Considering all species and sites, feathers (5.47 ± 2.15 μg/g) and bill sheath (3.39 ± 1.37 μg/g) had mean THg concentrations about 2-, 3- and 10-times higher than claws, liver and muscle, respectively. When bird species were segregated, the ringed kingfisher showed THg values 1.8 times higher than the Amazon kingfisher in all tissues. Moreover, results showed that the Amazon kingfisher from the Juruena and Teles Pires rivers was clearly separated from the Paraguay River (control site), and was associated with higher THg values in the claws and feathers. Results obtained for the THg concentrations in bill sheath, muscle and liver tissues of the Amazon kingfisher using multivariate analysis of canonical variates (CVA) showed a pattern of segregation between the sampling areas, being the highest THg values in Teles Pires River samples. The largest bill sheath vector in the CVA suggests that this tissue is a key variable in the segregation of the samples. Overall, feathers may be useful for effects monitoring or spatial patterns, whereas bill sheath, which are more invasive, may be advantejous for temporal trends and retrospective studies of Hg pollution.

Songbird feathers as indicators of mercury exposure: high variability and low predictive power suggest limitations

Although feathers are commonly used to monitor mercury (Hg) in avian populations, their reliability as a sampling matrix has not been thoroughly assessed for many avian species, including most songbirds (Order Passeriformes). To better understand relationships between total Hg (THg) concentrations in feathers and other tissues for birds in the thrush and sparrow families, we (1) examined variation in THg concentrations among tissues, including feathers from six different tracts, nails, liver, and muscle; (2) tested relationships between THg concentrations in the various feather tracts and those in internal tissues from the same birds, to assess the predictive power of feather THg, and; (3) compared these relationships to those between THg concentrations in nails and internal tissues, to assess the viability of nails as a non-lethal sampling alternative. THg concentrations in all feather tracts and nails were consistently higher than those in the liver and muscle, and THg was higher in the thrushes than the sparrows. When comparing feather tracts, we observed high variation within some individuals, suggesting that estimates of Hg exposure could vary depending on which feather was sampled. Despite this variation, feather type had little effect on the predictive power of feather THg concentrations, which ranged from extremely weak in the sparrows (0.09 ≤ R² ≤ 0.16) to moderate (0.29 ≤ R² ≤ 0.42) in the thrushes. Alternatively, we found that nail samples better predicted internal tissue THg concentrations in both the thrushes (0.44 ≤ R² ≤ 0.48) and sparrows (0.70 ≤ R² ≤ 0.78). Nails have been used to monitor Hg in mammals and reptiles, but their reliability as a sampling matrix for monitoring Hg in avian populations has yet to be assessed for most taxa. While nails exhibit stronger relationships to internal tissue THg concentrations, they may not be an effective sampling option for all avian species because the collection of sizable nail samples could harm living birds, particularly small songbirds. However, this method may be reasonable for retrospective museum studies. Overall, our results suggest that, despite their current use in the literature, feathers are not a suitable sampling matrix for Hg monitoring in some songbird species.

Intra-clutch and inter-colony variability in element concentrations in eggshells of the black-headed gull, Chroicocephalus ridibundus, in northern Poland

Eggshells are good bioindicators of environmental contamination, and therefore, the concentrations of 17 trace elements in 87 eggshells of black-headed gulls, Chroicocephalus ridibundus, were determined in five breeding colonies in an area dominated by farmland in northern Poland. The intra-clutch variability in the eggshell concentrations of heavy metals and other elements was also investigated, and the concentrations of the elements showed the following pattern: Ca > Mg > Sr > Fe > Zn > Al > Cr > Se > Mn > Cu > Pb > As > Ni > Mo = V > Sc > Cd. The concentrations of Fe, Al, and Mn decreased with the order in which the eggs were laid, but Sr concentrations increased. In contrast, the concentration of Cu significantly increased with the laying date. The concentrations of all elements significantly differed among the studied colonies; the highest concentration of eight elements was found in the eggshells from the Kusowo colony, which may have resulted from the intensive use of fertilizers, manure, and slurry in the surrounding agricultural region. The concentrations of Mg, Sr, and Zn in the eggshells from Skoki Duże were higher than those of the other studied colonies, which may have occurred because the gulls were nesting in a functioning gravel pit; soil and the parent rock are natural reservoirs of these elements. The observed element levels indicate that the environment where the black-headed gull eggs were formed, i.e., primarily near the breeding colonies, remains in a relatively unpolluted state, which was reflected by the low levels of Cd, Ni, and Pb and the lack of measurable levels of Hg.

Mercury in Feathers and Blood of Gulls from the Southern Baltic Coast, Poland

Gulls were assessed as sentinels of contamination in the coastal zone of the Southern Baltic, research material being obtained from dead birds collected on Polish beaches and near fishing ports in 2009-2012. In feathers and blood of four gull species: herring gull (Larus argentatus), common gull (Larus canus), black-headed gull (Chroicocephalus ridibundus), and great black-backed gull (Larus marinus), concentration of total mercury (HgT) was assayed, taking into account the type of feathers, sex, and age. Stable isotopes (δ15N, δ13C) were used as tracers of trophic position in the food web. In the study, feathers and blood were compared as non-invasive indicators of alimentary exposure introducing mercury into the system. In order to do that, the correlations between mercury concentrations in the blood, feathers, and the birds' internal tissues were examined. The strongest relations were observed in the liver for each species R2Common Gull = 0.94, p = 0.001; R2Black-headed Gull = 0.89, p = 0.001; R2Great Black-backed Gull = 0.53, p = 0.001; R2Herring Gull = 0.78, p = 0.001. While no correlation was found with feathers, only developing feathers of juvenile herring gulls were found to be a good indicator immediate of exposure through food (R2muscle = 0.71, p = 0.001; R2kidneys = 0.73, p = 0.001; R2heart = 0.89, p = 0.001; R2lungs = 0.86, p = 0.001; R2brain = 0.83, p = 0.001). Additionally, based on studies of herring gull primary feathers, decrease of mercury concentration in the diet of birds over the last two decades is also discussed.