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

Bowman, Timothy D.; Schempf, Philip F.; Bernatowicz, Jeffrey A.

doi:10.2307/3808945

Cited by 53 publications

(41 citation statements)

References 11 publications

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“…If true, an eventual decline of the breeding segment is predicted, unless (1) a supply of immigrant floaters is available to fill breeding vacancies, or (2) the current vital rate regime ameliorates. As expected, sensitivity analyses for both the matrix and life table models found the population most responsive to changes in adult survival and least affected by variation in juvenile survival and reproduction (Noon and Biles 1990, Bowman, Schempf, and Bernatowicz 1995, Hunt 1998). …”

Section: Moffat's Equilibrium Modelsupporting

confidence: 72%

“…We know of no such data for other populations of golden eagles. Therefore, let us examine the findings of Bowman et al (1995), who estimated the vital rates of the bald eagle (Haliaeetus leucocephalus) population at Prince William Sound, Alaska, following the Exxon Valdez oil spill. 1 Point estimates of survival rates were as follows: adults, 0.88; subadults, 0.95; and juveniles, 0.71.…”

Section: Discussionmentioning

confidence: 99%

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A Population Study of Golden Eagles in the Altamont Pass Wind Resource Area: Population Trend Analysis, 1994-1997

Hunt¹,

Jackman²,

Hunt³

et al. 1999

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ForewordAlthough the use of wind energy as an alternative electric generation source is now a viable choice, concern is still raised over the possible impacts of wind farms on birds. The concern includes two primary areas: the effect of avian mortality on bird populations, and possible litigation over the killing of even one bird if it is protected by the Migratory Bird Treaty Act, the Endangered Species Act, or both.The activities of the avian research program at the National Renewable Energy Laboratory (NREL) focuses on working towards minimizing the effects of wind turbines on birds and bird populations. NREL, funded by the U.S. Department of Energy, conducts research that (1) contributes to the refinement of the methods developed to assess impacts on the avian populations within wind farms, (2) seeks to understand how birds behave in and around wind turbines in different environments, (3) will try to identify how birds recognize wind turbines and develop recommendations for increasing the conspicuity of the turbines, and (4) will soon conduct acoustical research to develop acoustical deterrents where needed.The habitat surrounding the Altamont Pass Wind Resource Area (WRA) supports a substantial resident population of golden eagles (Aquila chrysaetos), perhaps one of the most dense ever recorded. Each year, the wind industry reports 28-43 golden eagles killed by turbine blade strikes in the Altamont WRA.NREL has supported the Santa Cruz Predatory Bird Research Group at the University of California, Santa Cruz, in conducting a golden eagle population study in the Altamont Pass WRA. The research, conducted over a four-year period, was designed to assess the impact of golden eagle deaths in the wind farm on the species' population survival and reproduction. This final report provides a detailed discussion of the data and research findings. Much has been learned during the first four years of this study. However, because the golden eagle is a long-lived species, the findings contained in this document are considered preliminary. Additional data collection over the next few years should provide a better understanding of how the golden eagle population is being impacted in the Altamont Pass WRA. EXECUTIVE SUMMARYThe Predatory Bird Research Group (PBRG), University of California, Santa Cruz, is conducting a long-term field study of the ecology of golden eagles (Aquila chrysaetos) in the vicinity of the Altamont Pass Wind Resource Area (WRA). The facility lies just east of San Francisco Bay in California and contains about 6,500 wind turbines on 190 km 2 of rolling grassland. Each year, the wind industry reports 28-43 turbine blade strike casualties of golden eagles in the WRA, and many more carcasses doubtless go unnoticed. Because golden eagles are naturally slow to mature and reproduce, their populations are sensitive to changes in adult and subadult survival rates. The U.S. Fish and Wildlife Service and the California Department of Fish and Game have therefore expressed concern that the fatalities might have an...

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Section: Moffat's Equilibrium Modelsupporting

confidence: 72%

Section: Discussionmentioning

confidence: 99%

A Population Study of Golden Eagles in the Altamont Pass Wind Resource Area: Population Trend Analysis, 1994-1997

Hunt¹,

Jackman²,

Hunt³

et al. 1999

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“…Populations of some bird species were apparently not reduced by the EVOS or recovered quickly (Bowman et al 1995, Wiens et al 1996. Black oystercatcher Haematopus bachmani breeding was depressed in 1989 to 1990 but nearly recovered by 1991 (Andres 1997).…”

Section: Conclusion and Recommendationsmentioning

confidence: 97%

Harlequin duck population recovery following the 'Exxon Valdez' oil spill: progress, process and constraints

Esler¹,

Bowman²,

Trust³

et al. 2002

Mar. Ecol. Prog. Ser.

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Following the 1989 'Exxon Valdez' oil spill in Prince William Sound, Alaska, we studied the status of recovery of harlequin duck Histrionicus histrionicus populations during 1995 to 1998. We evaluated potential constraints on full recovery, including (1) exposure to residual oil; (2) food limitation; and (3) intrinsic demographic limitations on population growth rates. In this paper, we synthesize the findings from our work and incorporate information from other harlequin duck research and monitoring programs to provide a comprehensive evaluation of the response of this species to the 'Exxon Valdez' spill. We conclude that harlequin duck populations had not fully recovered by 1998. Furthermore, adverse effects continued as many as 9 yr after the oil spill, in contrast to the conventional paradigm that oil spill effects on bird populations are short-lived. These conclusions are based on the findings that (1) elevated cytochrome P450 (CYP1A) induction on oiled areas indicated continued exposure to oil in 1998; (2) adult female winter survival was lower on oiled than unoiled areas during 1995 to 1998; (3) fall population surveys by the Alaska Department of Fish and Game indicated numerical declines in oiled areas during 1995 to 1997; and (4) densities on oiled areas in 1996 and 1997 were lower than expected using models that accounted for effects of habitat attributes. Based on hypothesized links between oil contamination and demography, we suggest that harlequin duck population recovery was constrained primarily by continued oil exposure. Full population recovery will also be delayed by the time necessary for intrinsic population growth to allow return to pre-spill numbers following cessation of residual oil spill effects. Although not all wildlife species were affected by the 'Exxon Valdez' oil spill, and some others may have recovered quickly from any effects, harlequin duck life history characteristics and benthic, nearshore feeding habits make them susceptible to both initial and long-term oil spill effects.

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“…Considering only the individuals that were alive and monitored (n = 38), 39.5% of the individuals older than 6 years were recorded as not yet territorial, suggesting the existence of a substantial fraction of adult floaters without breeding territories. Newton et al 1989, Bowman et al 1995. On the other hand, delayed maturity has been interpreted as an evolutionary strategy to gain useful experience and, in the long run, to increase individual fitness (Newton 1979).…”

mentioning

confidence: 99%

First Breeding Age in Captive and Wild Bearded VulturesGypaetus barbatus

Antor

Margalida²,

Frey

et al. 2007

Acta Ornithologica

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

Cited by 53 publications

References 11 publications

A Population Study of Golden Eagles in the Altamont Pass Wind Resource Area: Population Trend Analysis, 1994-1997

A Population Study of Golden Eagles in the Altamont Pass Wind Resource Area: Population Trend Analysis, 1994-1997

Harlequin duck population recovery following the 'Exxon Valdez' oil spill: progress, process and constraints

First Breeding Age in Captive and Wild Bearded VulturesGypaetus barbatus

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