Avian feathers as a biomonitoring tool to assess heavy metal pollution in a wildlife and bird sanctuary from a tropical coastal ecosystem

I believe I can fly… but in polluted air, why? Bird feathers as an example of environmental contaminant monitoring

Metallic element pollution is a global environmental problem, and it is important to study various local conditions to understand the mechanisms on a larger scale. Environmental contamination can be studied in many ways, but non-destructive techniques and methods that preserve the sample are increasingly gaining attention, especially in relation to studies on living organisms. The present study aimed to analyze the feathers of the great tit (Parus major) for Al, S, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ba and Hg content. Discriminant analysis showed that according to elemental composition young females and males make separate groups. At the same time, old birds are in the same group. From principal component analysis (PCA), elements distribution depends on age and gender and sources of elements can be natural and anthropogenic. However, not all element accumulation was dependent on both parameters: Al, Cr, Fe, and Ni were statistically significant from both parameters. Bird feathers can be regarded as promising biomonitors of air quality.

Blood, feathers, and eggs as bioindicators of selenium sources and their impact on DNA damage in Japanese quails (Coturnix japonica)

Selenium nanoparticles (Se-NPs), a nanoscale form of selenium, and sodium selenite (SS), an inorganic selenium compound, were incorporated into poultry feed to assess their effects on bioaccumulation, DNA damage, and cellular health. This study compared the effects of Se-NPs and SS on selenium bioaccumulation in blood, feathers, and eggs, along with their potential impact on DNA damage in quails. A total of 480 quails (14-day-old) were distributed into 5 groups. Each group consisted of 96 birds, arranged into 6 replicates (16 quails per replicate) with sex ratio 1 male: 3 females, 1st group as control, fed by basal diet; 2nd and 3rd group were supplemented with Se-NPs (0.2 mg/kg and 0.4 mg/kg), 4th and 5th groups were fed with SS (0.2 mg/kg and 0.4 mg/kg), respectively. The results showed that highest bioaccumulation occurred in blood, feathers, eggshells, and egg content in quails fed with higher doseage of Se-NPs. Maximum selenium bioaccumulation was found in eggshells due to their porous structure. Quails treated with Se-NPs (0.4 mg/kg) and SS (0.2 mg/kg and 0.4 mg/kg) exhibited DNA damage, with more pronounced adverse effects observed in groups receiving SS. The correlation between groups and DNA damage was noted, there is positive correlation between Length of Head (LHead), Length of Tail (LTail) and Length of Comet (LComet) parameters related to different groups of quails. The study indicated that while Se-NPs led to the highest bioaccumulation, they were less harmful in terms of DNA damage compared to SS.

Heavy metal concentrations in feathers and metabolomic profiles in Pacific black ducks (Anas superciliosa) from Southeastern Australia

Heavy metals are cumulative toxicants that frequently create negative health effects for waterbirds inhibiting contaminated freshwater systems. Although levels of exposure to heavy metals have been well documented for many waterbird species, the adverse effects of exposure remain relatively poorly understood. One emerging field that allows the exploration of such effects is metabolomics. The aim of this study was to characterize metabolomic profiles in relation to long-term heavy metal exposure in a waterbird species. In 2021, wings from 44 Pacific black ducks (Anas superciliosa) were collected by recreational hunters at three sites in Victoria, southeastern Australia. The concentrations of seven heavy metals were measured in feathers and these data were quantified via inductive coupled plasma mass spectrometry and compared with a semiquantitative assessment of 21 metabolites identified in muscle tissues from the same birds via gas chromatography-mass spectrometry. Principal component analysis was conducted to test associations between metabolites, heavy metals, and sites. Mean heavy metal concentrations detected were copper (9.97 µg/g), chromium (0.73 µg/g), iron (123.24 µg/g), manganese (13.01 µg/g), mercury (0.58 µg/g), lead (0.86 µg/g), and zinc (183.95 µg/g; dry wt). No association was found between heavy metals and 17 metabolites, whereas four metabolites were negatively associated with some heavy metals: α-linolenic acid with iron, glucose with lead and manganese, lactic acid with mercury, and propanoic acid with mercury. There were few differences in the studied metabolites in ducks between the three sites. This study provides a novel approach to combining toxicological and metabolomic data for an ecologically important species from a relatively poorly studied global region.

Persistent organic pollutants in feathers of various terrestrial and aquatic bird species: Interspecies difference and source apportionment

Feathers are regarded as important nondestructive biomonitoring tools for bird pollutants. However, external contamination of feathers by different pollutants in different bird species remains unclear. In the present study, the feathers of 16 bird species, including terrestrial, freshwater, and marine birds, were analyzed for persistent organic pollutants (POPs). Bird feathers from an abandoned e-waste recycling site had higher POP concentrations and were more correlated with the POP muscle concentrations than those from the less polluted areas. The significant and positive POP correlations between the feathers and muscles of different species indicate that feathers are a good indicator of inter-species and spatial pollution. For individual species, the most hydrophobic POPs in feathers, such as hepta- to deca-polybrominated diphenyl ethers, had higher proportions than in muscles and worse correlations with muscle POPs compared with other POPs. Results of the chemical mass balance (CMB) model revealed that the gaseous phase, internal pollution, and atmospheric particle phase were the main contributors to low-, medium-, and high-hydrophobicity POPs in feathers, respectively. Overall, this study provides a preliminary but meaningful framework for distinguishing between internal and external contamination in feathers and gives information concerning the fitness of feathers as POP indicators with specific physicochemical properties.

Species Differences and Tissue Distribution of Heavy Metal Residues in Wild Birds

Birds are useful as bioindicators of metal pollution, but the variety of species and tissue distribution may influence the study of heavy metal burdens in birds. The objective of this study was to determine the levels of heavy metals in wild birds' carcasses to acquire information on species differences and the tissue distribution of metals in wild birds in Thailand. Species differences in metal buildup were observed in the livers and kidneys, but not in the feathers. A significantly higher accumulation of Cd was found in the livers and kidneys of the granivorous birds compared to those in the water birds. In all the groups of birds, the Pb level in the livers (>15 ppm) and feathers (>4 ppm) exceeded the threshold limits, causing potential lead poisoning and disturbing the reproductive success. The Cd accumulation in the kidneys was above 2-8 ppm, indicating increased environmental exposure to Cd in these birds. The Cd, Pb, Ni, Zn, and Fe concentrations in the livers could be estimated using the kidneys, while the Pb level in the liver may be predicted using feathers. Furthermore, water birds' feathers may be potentially appropriate bioindicators for long-term exposure. Research on the origin of metal contamination is needed to reduce the threat of heavy metals to the health of both birds and other wildlife species.

Mercury in Neotropical birds: a synthesis and prospectus on 13 years of exposure data

Environmental mercury (Hg) contamination of the global tropics outpaces our understanding of its consequences for biodiversity. Knowledge gaps of pollution exposure could obscure conservation threats in the Neotropics: a region that supports over half of the world's species, but faces ongoing land-use change and Hg emission via artisanal and small-scale gold mining (ASGM). Due to their global distribution and sensitivity to pollution, birds provide a valuable opportunity as bioindicators to assess how accelerating Hg emissions impact an ecosystem's ability to support biodiversity, and ultimately, global health. We present the largest database on Neotropical bird Hg concentrations (n = 2316) and establish exposure baselines for 322 bird species spanning nine countries across Central America, South America, and the West Indies. Patterns of avian Hg exposure in the Neotropics broadly align with those in temperate regions: consistent bioaccumulation across functional groups and high spatiotemporal variation. Bird species occupying higher trophic positions and aquatic habitats exhibited elevated Hg concentrations that have been previously associated with reductions in reproductive success. Notably, bird Hg concentrations were over four times higher at sites impacted by ASGM activities and differed by season for certain trophic niches. We developed this synthesis via a collaborative research network, the Tropical Research for Avian Conservation and Ecotoxicology (TRACE) Initiative, which exemplifies inclusive, equitable, and international data-sharing. While our findings signal an urgent need to assess sampling biases, mechanisms, and consequences of Hg exposure to tropical avian communities, the TRACE Initiative provides a meaningful framework to achieve such goals. Ultimately, our collective efforts support and inform local, scientific, and government entities, including Parties of the United Nations Minamata Convention on Mercury, as we continue working together to understand how Hg pollution impacts biodiversity conservation, ecosystem function, and public health in the tropics.

Biomonitoring of heavy metals and their association with DNA damage in Indian peafowl (Pavo cristatus) under captivity

Environmental pollution and changing climatic conditions are likely to damage biodiversity not only on organismal level but on molecular level as well. The aim of the present study was to find the concentration of heavy metals in soil, water, feed, feathers, and blood and association of heavy metals with DNA damage of P. cristatus. The results showed that lead (Pb) was significantly (P < 0.01) higher in soil and cadmium (Cd) was significantly (P < 0.01) higher in soil and water. Chromium (Cr), zinc (Zn), nickel (Ni), and cobalt (Co) were significant (P < 0.01) in feed. Manganese (Mn) was significantly (P < 0.01) higher in feed and soil (surface). In addition, Pb and Cd concentrations were significant (P < 0.01) in feathers while Cr and Zn concentrations were significantly (P < 0.01) higher in feces. Nickel was significantly (P < 0.01) higher in feathers and eggshell while Mn and Co concentrations were significantly (P < 0.01) higher in blood and feces, respectively. Furthermore, significant positive correlation between Pb (r_s = 0.75; P < 0.05) and Cd (r_s = 0.67; P < 0.05) concentrations in blood with tail DNA was found. It was concluded that heavy metals exist in the soil, water, feathers, and blood and have association with DNA damage of P. cristatus.