INFLUENCE OF LOW-LEVEL CADMIUM AND REDUCED CALCIUM INTAKE ON TISSUE CD CONCENTRATIONS AND BEHAVIOR OF AMERICAN BLACK DUCKS

Populations of American black ducks have declined and if has been hypo thesized that wetland acidification, which can alter food quality by i ncreasing availability of cadmium and decreasing that of calcium, may have contributed. We tested whether low-level cadmium and reduced calc ium intake affect tissue cadmium concentrations and behaviour of capti ve black ducks. Adults received diets that mimicked cadmium and calciu m concentrations in invertebrate prey from acid and from circumneutral wetlands for three spring and slimmer months in 1991 and 1992. Behavi ours were monitored both when birds were fed experimental diets and co ntrol (commercial) diets. Cadmium in kidneys and liver differed signif icantly among groups and low calcium facilitated cadmium uptake. After two breeding seasons, levels of accumulated Cd were not lethal. Howev er, birds that received Cd were significantly more active than control birds. Increased activity may have implications for survival of birds in the wild.