Feather heavy metal contamination in various species of waterbirds from Asia: a review.

The amounts of certain heavy metals in waterfowl fluctuate depending on a number of factors. The use of feathers in heavy metal contamination studies is gaining popularity for several reasons, including the lack of need for deep freezing for sample preservation, the fact that it is a non-destructive, non-invasive method that does not require killing an individual, and the ability to predict lead and cadmium concentrations in internal tissues. A total of 22 publications from eight Asian countries including Pakistan, China, Hong Kong, India, Iran, South Korea, Indonesia, and Japan were identified and analysed in this study. The highest number of study sites were found from Pakistan (n = 12), followed by China (n = 9), Hong Kong, South Korea, and India (n = 7) each. A total of 10 heavy metals, viz cadmium, chromium, lead, copper, nickel, zinc, iron, mercury, selenium, and arsenic, have been identified for the review. Mercury (0.17-79.66 ppm) has been studied in all 44 species, whereas selenium (0.98-4.88 ppm) has only been studied in five species. Mercury (8.6 ppm) contamination is highest in Painted Stork from India. Cadmium, lead, copper, and arsenic contamination was detected in the highest concentrations in Cattle Egret and Indian Pond Heron. The highest contamination of cadmium (41.1 ppm), lead (296 ppm), and arsenic (20 ppm) were found in Cattle Egret from Pakistan. Chromium, nickel, and zinc contamination was highest in waders such as Marsh Sandpiper (114.7 ppm), Little Ringed Plover (114.8 ppm), and Little Stint (328.4 ppm), respectively from India. Black-tailed Gull from South Korea had the highest contamination of Iron (4055.55 ppm) and selenium (7.55 ppm). Feather analysis is not an alternative of internal tissue analysis. It should be considered as an initial warning of the hazardous effects of the heavy metals in the waterbirds.