skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: High rates of nonbreeding adult bald eagles in southeastern Alaska

Abstract

Present knowledge of bald eagle (Haliaeetus leucocephalus) demography is derived primarily from populations in environments that have been drastically altered by man. Most reproductive studies were done in the 1960's and 1970's when chemical toxins were inhibiting bald eagle productivity. Earlier, the removal of old-growth forests and decimation of anadromous fish runs by Euro-Americans may have greatly reduced bald eagle abundance from presettlement levels. Historical trends in this species are of interest because fundamental differences may exist between populations in pristine and man-altered environments. One difference may be breeding rate. Surpluses of nonbreeding adult bald eagles during the nesting season are rarely mentioned in the literature. Most surveys of reproductive success focus exclusively on eagles at nest sites, which assumes nearly all adults attempt to breed each year. The authors report that a majority of adults in the relatively pristine habitats of southeastern Alaska do not breed annually. This finding is important because if surpluses of non-breeding adults are a natural feature of the population, then hypotheses on density dependent population regulation and the evolution of delayed maturation are suggested. If, on the other hand, the abundance of nonbreeders is an artifact of recent environmental perturbations, serious population declines maymore » occur in southeastern Alaska.« less

Authors:
;
Publication Date:
Research Org.:
Fish and Wildlife Service, Juneau, AK
OSTI Identifier:
5558371
DOE Contract Number:
AC05-84OR21400
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Wildl. Manage.; (United States); Journal Volume: 49:2
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; BIRDS; BIOLOGICAL ADAPTATION; REPRODUCTION; ALASKA; ANIMAL BREEDING; ENDANGERED SPECIES; ANIMALS; FEDERAL REGION X; NORTH AMERICA; USA; VERTEBRATES; 560305* - Chemicals Metabolism & Toxicology- Vertebrates- (-1987)

Citation Formats

Hansen, A.J., and Hodges, J.I. Jr. High rates of nonbreeding adult bald eagles in southeastern Alaska. United States: N. p., 1985. Web. doi:10.2307/3801551.
Hansen, A.J., & Hodges, J.I. Jr. High rates of nonbreeding adult bald eagles in southeastern Alaska. United States. doi:10.2307/3801551.
Hansen, A.J., and Hodges, J.I. Jr. Tue . "High rates of nonbreeding adult bald eagles in southeastern Alaska". United States. doi:10.2307/3801551.
@article{osti_5558371,
title = {High rates of nonbreeding adult bald eagles in southeastern Alaska},
author = {Hansen, A.J. and Hodges, J.I. Jr.},
abstractNote = {Present knowledge of bald eagle (Haliaeetus leucocephalus) demography is derived primarily from populations in environments that have been drastically altered by man. Most reproductive studies were done in the 1960's and 1970's when chemical toxins were inhibiting bald eagle productivity. Earlier, the removal of old-growth forests and decimation of anadromous fish runs by Euro-Americans may have greatly reduced bald eagle abundance from presettlement levels. Historical trends in this species are of interest because fundamental differences may exist between populations in pristine and man-altered environments. One difference may be breeding rate. Surpluses of nonbreeding adult bald eagles during the nesting season are rarely mentioned in the literature. Most surveys of reproductive success focus exclusively on eagles at nest sites, which assumes nearly all adults attempt to breed each year. The authors report that a majority of adults in the relatively pristine habitats of southeastern Alaska do not breed annually. This finding is important because if surpluses of non-breeding adults are a natural feature of the population, then hypotheses on density dependent population regulation and the evolution of delayed maturation are suggested. If, on the other hand, the abundance of nonbreeders is an artifact of recent environmental perturbations, serious population declines may occur in southeastern Alaska.},
doi = {10.2307/3801551},
journal = {J. Wildl. Manage.; (United States)},
number = ,
volume = 49:2,
place = {United States},
year = {Tue Jan 01 00:00:00 EST 1985},
month = {Tue Jan 01 00:00:00 EST 1985}
}
  • The Columbia River at the Hanford Site is a regionally important refugium for overwintering birds. Some of the river shoreline has been designated by the U.S. Department of Energy for environmental clean-up following past production of materials for nuclear weapons. We evaluated the effects of soil remediation on winter birds at six inactive nuclear reactor areas. Remediation activities consisted of daily removal of approximately 1,035 t of contaminated soil from previously herbicided and denuded areas located between 30 m and 400 m and in partial line-of-sight of the river shoreline. Remediation activities had no apparent effect on numbers of riverinemore » or terrestrial birds using adjacent undisturbed shoreline and riparian habitat.« less
  • Eggs, blood, and carcasses of bald eagles (Haliaeetus leucocephalus) and fish were collected and breeding success of eagles was monitored in the Columbia River estuary, 1980-87, to determine if contaminants were having an effect on productivity. High levels of dichloro diphenyl dichloroethylene (DDE), polychlorinated biphenyls (PCB's), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were found in eggs, blood from adults, and 2 eagle carcasses. Detectable levels of DDE and PCB's were found in blood of nestlings indicating they were exposed to these contaminants early in life. Increasing concentrations of DDE and PCB's with age also indicated accumulation of these contaminants. Adult eagles also hadmore » higher levels of mercury (Hg) in blood than subadults or young indicating accumulation with age. The high levels of DDE and PCB's were associated with eggshell thinning ([bar x] = 10%) and with productivity ([bar x] = 0.56 young/occupied site) that was lower than that of healthy populations (i.e., [ge]1.00 young/occupied site). DDE and PCB's had a deleterious effect on reproduction of bald eagles in the estuary. The role dioxins play in eagle reproduction remains unclear, but concentrations in eagle eggs were similar to those in laboratory studies on other species where dioxins adversely affected hatchability of eggs. Probable source of these contaminants include dredged river sediments and hydroelectric dams, and the proper management of each may reduce the amount of contaminants released into the Columbia River estuary. 46 refs., 1 fig., 4 tabs.« less
  • We investigated the relationship between diets and potential hazards in contaminants of wintering bald eagles (Haliaeetus leucocephalus) in the Klamath Basin of northern California and southern Oregon. We studied diets by identifying remains of 913 prey items found at perches, examining 341 castings collected from communal night roots, and observing foraging eagles. We determined residues of organochlorine compounds, lead (Pb), and mercury (Hg) in bald eagles and their prey by analyzing eagle blood samples and carcasses and 8 major prey species. Bald eagles fed largely on waterfowl by scavenging cholera-killed ducks and geese and on microtine rodents during mid- tomore » late winter. Residues of organochlorine pesticides and Hg in prey were low, and polychlorinated biphenyls (PCB's) were detected in low concentrations in 9% of prey samples. Means Pb concentrations in prey ranged from 0.15 to 4.79 ppm. Mercury was detected in all eagle blood samples, and Pb was detected in 41% of the bald eagle blood samples. Mean Pb concentration in livers of dead eagles was 2.09 ppm and ranged as high as 27 ppm in an eagle that died of Pb poisoning. Prey of the eagles were relatively free of contaminants with the possible exception of embedded Pb shot in waterfowl, which may present a potential for Pb poisoning of eagles.« less
  • We collected 48 blood and 61 feather samples from nestling bald eagles at 42 nests and adult feather samples from 20 nests in north and central Florida during 1991-93. We obtained 32 liver, 10 feather, and 5 blood samples from 33 eagle carcasses recovered in Florida during 1987-93. For nestlings, mercury concentrations in blood (GM = 0.16 ppm wet wt) and feather (GM = 3.23 ppm) samples were correlated (r = 0.69, P = 0.0001). Although nestlings had lower mercury concentrations in feathers than did adults (GM = 6.03 ppm), the feather mercury levels in nestlings and adults from themore » same nest were correlated (r = 0.63, P < 0.02). Mercury concentrations in blood of captive adult eagles (GM = 0.23 ppm) was similar to Florida nestlings but some Florida nestlings had blood mercury concentrations up to 0.61 ppm, more than twice as high as captive adults. Feather mercury concentrations in both nestlings and adults exceeded those in captive eagles, but concentrations in all tissues were similar to, or lower than, those in bald eagles from other wild populations. Although mercury concentrations in Florida eagles are below those that cause mortality, they are in the range of concentrations that can cause behavioral changes or reduce reproduction. We recommend periodic monitoring of mercury in Florida bald eagles for early detection of mercury increases before negative effects on reproduction occur. 26 refs., 5 figs., 2 tabs.« less
  • This article describes the controversy between the US Fish and Wildlife Service, the National Wildlife Federation and the increased mortality of bald eagles. The eagles are being poisoned by preying on waterfowl which have ingested lead shot or have been wounded by shot and not recovered. The controversy has resulted in the establishment of new criteria for so-called non-toxic shot waterfowl hunting.