Heavy metal and selenium concentrations in black skimmers (Rynchops niger): gender differences.

Most studies of heavy metals and selenium have not examined or have failed to find differences in concentrations in the tissues of birds as a function of size or sex. Heavy metal and selenium concentrations were analyzed in breast feathers of adult black skimmers Rynchops niger, a species with marked sexual size dimorphism in which males average 35% heavier than females. Females had significantly higher concentrations of lead and cadmium than males, but there were no gender differences in mercury, selenium, chromium, manganese, and copper despite the marked sexual dimorphism in body size. There were no significant correlations of bird weight or wing length and metal and selenium concentrations, and few correlations among metal and selenium concentrations in the feathers.