Survival Probability and Mortality of Migratory Juvenile Golden Eagles from Interior Alaska

Abstract

The conservation of golden eagles (Aquila chrysaetos) requires a thorough understanding of their demographic parameters. Productivity, commonly measured as the number of nestlings or fledglings per pair, is the parameter reported by most studies of nesting golden eagles and is often used as a measure of their population status. Survival may be an equally or more important parameter to measure; however, survival rates of golden eagles are not well documented. We used satellite telemetry to estimate the probability of first-year survival for migratory golden eagles raised in Denali National Park and Preserve, Alaska, USA. We calculated the probability of first-year survival using program MARK. Based on the best approximating model, monthly survival probability was 0.88 ± 0.04 (mean ± SE) during the autumn migration and early winter period for golden eagles marked in 1997 and 0.78 ± 0.05 during the same period for golden eagles marked in 1999. Monthly survival during the remaining 3 periods (i.e., late winter, spring migration, summer) was 0.94 ± 0.03 for both cohorts. Survival during the entire 11-month period was 0.34 ± 0.10 for the 1997 cohort and 0.19 ± 0.07 for the 1999 cohort. Causes of mortality included starvation, electrocution, and poaching. Our results indicate that low first-year survival may limit recruitment and we recommend that golden eagle monitoring programs include survival estimates.