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 Alaska Peninsula between 1975-97. We used mark-recapture analysis techniques to estimate annual survival and movement probabilities within and among lagoons 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 showed high rates of fidelity to specific molting locations (>95%) within lagoons; yet we found no evidence that annual probability of survival differed among groups molting in different locations either within or among lagoons. We found weak evidence that annual survival decreased between thr periods 1875-81 and 1991-97. The lower survival of males compared to females is unusual 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 population decline. Further, a shortage of males may be limiting reproductive potential.