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

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.