ELEMENTAL PROFILES IN FEATHER SAMPLES FROM A MERCURY-CONTAMINATED LAKE IN CENTRAL CALIFORNIA

Flight feathers from six bird species at Clear Lake, CA were analyzed to determine the extent and distribution of mercury contamination from an abandoned mercury mine and associated levels of 14 other elements. Feather samples were collected from adult and juvenile osprey (Pandio n haliaetus), including juvenile osprey from three additional comparis on sites; adult western grebes (Aechmophorus occidentalis); adult grea t blue herons (Ardea herodias); adult mallards (Anas platyrhynchos); a dult turkey vultures (Cathartes aura); and juvenile double-crested cor morants (Phalacrocorax auritus). Samples were analyzed by a multieleme ntal x-ray fluorescence method. The osprey from Clear Lake showed sign ificantly elevated mercury concentrations relative to the comparison s ites, Different species at Clear Lake had different mercury concentrat ions based on trophic status; osprey exhibited the highest mercury con centrations and the mallards showed the lowest, Lastly, we quantified differences in elemental concentrations, including mercury, between ad ult and juvenile osprey from Clear Lake. Elements known to be nutrient s, such as sulfur and zinc, did not vary significantly among species o r sites. Reproductive success of osprey at Clear Lake was monitored fr om 1992 to 1996 to determine if osprey reproduction was depressed. Dur ing this five-year period, the breeding population grew from 10 to 20 nesting pairs and the average reproductive rate was 1.4 fledglings per nesting attempt. Although the osprey showed the highest mercury level s of any species sampled, their reproduction does not appear to be dep ressed.