Golden Eagles (Aquila chrysaetos) were banded as nestlings, migrants, wintering birds, and resident breeders in three states of the U.S. Rocky Mountain West between June 1973 and January 1999. To January 2000, 6.2% of 325 eagles banded had been encountered as dead or injured birds or live captures. Median age of all encounters was 2.25 yr. Sex ratio of Golden Eagles encountered was not different from sex ratio at banding. Eagles banded as migrants were encountered less frequently than those banded as nestlings, residents, or wintering eagles. Cumulative exponential distribution analysis of recoveries (dead eagles) by age indicated 50% of banded eagles were dead by 2 yr, 7 mo, 75% by age 5 yr, 1 mo, and 95% by 11 yr, 1 mo, with a maximum predicted age of 33 yr, 10 mo. Distance from banding to encounter site was <90 km for 90% of encounters, and all encounters of eagles banded as nestlings were within 200 km of their natal nest. Mean vector bearing of all encounters was 92.95°. Rayleigh tests for uniformity indicated encounters showed no directional bias, but only 22% of all encounters were westward. No encounters occurred on the slope of the Continental Divide opposite from banding. The largest proportion (40%) of Golden Eagles encountered died of unknown causes, and eagles less than one-year old may suffer the highest mortality rate. Considering the minimal contribution of recent nestling banding to the understanding of Golden Eagle demography and natural history, conservation and management of the species may be better served by focusing on more productive methods of research (color-marking, radio-tagging) rather than simply banding nestlings.
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Vol. 73 • No. 1