A COMPARISON OF MERCURY LEVELS IN FEATHERS AND EGGS OF OSPREY (PANDION HALIAETUS) IN THE NORTH-AMERICAN GREAT-LAKES

Osprey (Pandion haliaetus) eggs and chick feathers were collected for mercury analysis from nests at four Great Lakes study areas in Ontario (three ''naturally formed'' lakes in southern Ontario and one reservo ir in northern Ontario) and two New Jersey study areas in 1991-1994. A dult osprey feathers were sampled from three Great Lakes study areas i n 1991. Feathers sampled from chicks (approximately 28-35 days old) ap pear to be better indicators of local contaminant conditions since spa tial patterns of mercury in known prey, yellow perch (Perca flavescens ), also collected in these areas, were more similar to chick feathers than to eggs. Mercury levels were less variable in chick feathers than in eggs. Estimates of biomagnification factors using prey of known si ze at these areas were also less variable in feathers than in eggs. At naturally formed lakes, no significant correlation in mercury levels between eggs and chick feathers from the same nest was apparent, sugge sting that the source of mercury contamination was not the same in the se two tissues: mercury levels in eggs reflect mercury acquired on the breeding grounds, wintering grounds, and migratory route; mercury lev els in chick feathers reflect local dietary conditions on the breeding grounds. Mercury levels in both osprey eggs and chick feathers were h igher at the Ogoki Reservoir than at naturally formed lakes. Adult osp rey feathers had higher mercury concentrations than chick feathers. Me rcury levels in osprey eggs, chick feathers, and adult feathers did no t approach levels associated with toxic reproductive effects.