Late summer survival of adult female and juvenile Spectacled Eiders on theYukon-Kuskokwim Delta, Alaska

We used radio-telemetry; to examine survival of adult female and juvenile S pectacled Elders (Somateria fischeri) from 30 days after hatch until depart ure from the Yukon-Kuskokwim Delta (YKD) during 1997-1999. Juvenile surviva l was 71.4%; adult female survival was 85.5%. Mink (Mustella vison) were th e most common predator identified for both adults and juveniles. Detectable levels of lead were found in bones of 74% of juvenile carcasses recovered and 21% had. levels indicative of acute exposure, Average age at departure was 59 +/- 1 days old for juveniles and 56 +/- 1 days after hatch for adult s. Most broods (60.5%) departed the YKD synchronously. Overall our data ind icate that mortality during the latter half of brood-rearing is higher than previously thought. We conclude that brood rearing is a period of high mor tality for brood-rearing females and that lead poisoning is responsible for reductions in juvenile survival to fledging.