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• Heavy metals in waterbirds from the Magela Creek flood plain, Alligator Rivers Region, Northern Territory, Australia (PDF 786 KB)

About the report

Baseline information is provided on the pre-mining levels of cadmium, chromium, copper, lead, manganese, nickel and zinc in the primary feathers, pectoral muscle, and liver of 22 species of waterbirds that occur commonly on the Magela Creek flood plain. The ranges of mean metal concentrations (geometric mean, µg/g dry weight) in liver were: cadmium 0.013-1.3 µg/g (blackwinged stilt [species with highest mean cadmium concentration in liver]), copper 51-2500 µg/g (green pygmy goose), lead 0.015-0.43 µg/g (comb-crested jacana), manganese 19-61 µg/g (little pied cormorant) and zinc 260-630 µg/g (wandering whistling duck). The Pacific black duck had the highest total metal content in liver.

Metal concentrations in the three tissues were not equivalent in any species, but the overall pattern of variation was similar for all species for each metal. Concentrations in feathers were lower than for liver (see above) but higher than in muscle. No quantitative relationship was found between metal levels in different tissues, nor was any pattern of variation found between species - related to sexual, seasonal or dietary factors. The tissue and organ concentrations of most metals were comparable with, or lower than, metal levels reported from waterfowl in 'pristine' environments elsewhere. Cadmium and lead levels were very low but zinc concentrations were found to be high relative to other literature values. The problems of determining the sources of accumulated metals in waterbirds are briefly discussed.

Feathers have proved poor predictors of metal levels in either muscle or liver, furthermore it has been clearly demonstrated that concentrations in feathers may not reflect the degree of physiological exposure. So the use of feathers as monitors of metals in waterbirds is very limited.

The waterfowl species utilised as food by Aboriginal people contained metal levels either within prescribed NH & MRC food standards or, where they exceeded them (i.e. copper in green pygmy goose liver), the possibility of a health risk to humans is considered remote.