Movements and survival of bald eagles banded in the greater yellowstone ecosystem

Movements and survival of immature Laid eagles (Haliacetus leucocephalus) b eyond their first winter remain largely unknown, and lack of information ma y impede strategies for effective conservation. We analyzed encounters, sig htings, and radio detections of bald eagles auxiliary marked as nestlings i n the Greater Yellowstone Ecosystem (GYE) between June 1979 and July 1987 t o determine movements, survival, and role of Yellowstone National Park in t he ecology of CTE bald eagles. Of 344 bald eagles Landed, 17% were encounte red to June 1998. Most (84%) were encounters of bald eagles >1 year old. Ha lf of encounters were external to the GYE and occurred in 7 western states and 1 Canadian province. All sightings of color-landed bald eagles (n = 76) were of bald eagles >1 year old, and 76% occurred in the GYE. Location and timing of encounters and detections of radiotagged bald eagles indicated m ost (>90%) juveniles left the GYE in autumn, traveled as far west as coasta l stales to winter, and returned to natal areas the following spring. Natal dispersal appeared female-biased, and bald eagles produced in the GYE recr uited into breeding populations both in and out of the ecosystem. Mortality of 49 bald eagles recovered was from unknown causes (31%), electrocution o r collision with power lines (20%), known or suspected poisoning (16%), and gunshot wounds (14%). Eighteen percent was distributed among 3 other cause s. Recovery rates indicated Laid eagles 3-5 years old experienced the highe st mortality Kaplan-Meir analysis of detections of radiotagged Laid eagles indicated first-lear survival of 87%, followed by a constant decrease in su rvival rate over 7 years. Survival estimates determined by radio-tracking w ere consistent Midi Land recovery results in illustrating low survival in 3 - to 5-year-old age classes. Radiotracking of immature bald eagles suggeste d habitat in Yellowstone National Park was important in promoting survival of eventual recruits to the GYE population.