Heavy Metal and Selenium Concentrations in Feathers of Egrets from Bali and Sulawesi, Indonesia

Abstract.

Herons and egrets are ideal organisms to use as indicators of heavy metal exposure in an ecosystem because different species feed at different levels of the food chain and live in both coastal and inland habitats. This paper reports on the concentration of heavy metals and selenium in the feathers of cattle egrets Bubulcus ibis that were examined from nesting and roosting sites in Bali and Sulawesi, Indonesia, and in feathers of little egrets Egretta garzetta and intermediate egrets E. intermedia from the same colony in Bali. Mercury and manganese concentrations were significantly higher in cattle egrets from Bali compared to Sulawesi, but otherwise there were no significant differences. There were significant differences in lead, cadmium and mercury among the three egret species nesting on Bali: 1) the cadmium and mercury concentrations related to size and trophic level (insectivorous cattle egrets had the lowest concentrations, fish-eating intermediate egrets had the highest concentrations), and 2) cattle egrets had significantly lower concentrations of lead than the other two species. For cattle egrets, secondary flight feathers had significantly higher levels of cadmium and mercury, and lower levels of manganese, than mixed breast and tertiary feathers, reflecting temporal differences in exposure.