HEAVY-METAL AND SELENIUM LEVELS IN FEATHERS OF KNOWN-AGED COMMON TERNS (STERNA-HIRUNDO)

Concentrations of five metals and selenium in the breast feathers of k nown-aged common terns (Sterna hirundo) were examined at a breeding co lony in Massachusetts, USA. Concentrations of selenium, chromium, and manganese increased significantly with age among adults (2-21 years ol d), whereas concentrations of mercury, cadmium, and lead did not. Conc entrations of cadmium, selenium and manganese were lower in fledglings (20-23 days old) than in adults. Concentrations of mercury, however, were higher in fledglings than in adults, and concentrations of chromi um were higher in fledglings than in young adults, probably reflecting higher exposure to these metals in the breeding area than in the wint er quarters where the adults' feathers were grown. At least for mercur y, excretion of metals into the feathers at each molt was an efficient protective mechanism, preventing continued accumulation in the body w ith increasing age.