Annual survival and site fidelity of Steller's eiders molting along the Alaska Peninsula

Populations of Steller's elders (Polysticta stelleri) molting and wintering along die Alaska Peninsula have declined since the 1960's. We captured and marked a large sample of Steller's elders molting in 2 lagoons along the A laska Peninsula between 1975-97. We used mark-recapture analysis techniques to estimate annual survival and movement probabilities within and among la goons for male and female elders. Estimates of annual survival (+/-SE) were 0.890 +/- 0.032 for females and 0.765 +/- 0.044 for males. Both sexes show ed high rates of fidelity to specific molting locations (>95%) within lagoo ns; yet we found no evidence that annual probability of survival differed a mong groups molting in different locations either within or among lagoons. We found weak evidence that annual survival decreased between thr periods 1 875-81 and 1991-97. The lower survival of males compared to females is unus ual for water fowl and may result in a female-biased sex ratio. We conclude that a decrease in adult survival may have initiated the long-term populat ion decline. Further, a shortage of males may be limiting reproductive pote ntial.