Monday, 28 February 2011

Bald Eagle Survival and Population Dynamics in Alaska after the" Exxon Valdez" Oil Spill

Bald Eagle Survival and Population Dynamics in Alaska after the
The Journal of Wildlife Management © 1995 Allen Press


We investigated age-specific annual survival rates for 159 bald eagles (Haliaeetus leucocephalus) radiotagged from 1989 to 1992 in Prince William Sound (PWS), Alaska. We monitored radio-tagged eagles for ≤3 years beginning 4 months after the Exxon Valdez oil spill. There was no difference (P > 0.10) in survival rates between eagles radiotagged in oiled areas and eagles radiotagged in unoiled areas of PWS. Pooled annual survival rates were 71% for first-year eagles, 95% for subadults, and 88% for adult bald eagles. Most deaths occurred from March to May. We found no indication that survival of bald eagles radiotagged >4 months after the oil spill in PWS was directly influenced by the spill and concluded that any effect of the spill on survival occurred before eagles were radiotagged. A deterministic life table model suggests that the PWS bald eagle population has an annual finite growth rate of 2%. Given the cumulative effects of direct mortality and reduced productivity caused by the oil spill, we predicted that the bald eagle population would return to its pre-spill