Graduate Thesis Or Dissertation
 

Environmental contaminants and ecology of bald eagles in southcentral Oregon

Público Deposited

Conteúdo disponível para baixar

Baixar PDF
https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/rv042w30g

Descriptions

Attribute NameValues
Creator
Abstract
  • Food habits and levels of organochlorine compounds, lead, and mercury in resident and wintering bald eagles were studied in southcentral Oregon and California, 1979-83. Food habits were assessed by examination of castings from winter communal roosts, identification of 2938 prey items found at nest sites and foraging areas, and observations of 16 eagles with radios. Contaminant residues in prey were determined by analyses of 290 pooled samples of potential prey. Contaminant residues in eagles were determined by analyses of 13 addled eggs, blood samples from 24 adults, 8 sub-adults, and 82 nestlings, and carcasses of 11 eagles. Non-resident eagles concentrated in the southern Klamath Basin during winter months and fed largely on microtine rodents and cholera-killed dabbling ducks and geese. Contaminant residues in samples of prey from the wintering area were low with the possible exception of lead shot in waterfowl, which presented a potential for lead poisoning in eagles. Wintering bald eagles did not have elevated body burdens of organochlorines which have been associated with reproductive problems. Diets of resident eagles in southcentral Oregon were highly diverse, changed seasonally, and differed markedly by geographic region. Eagles fed largely on fish during summer months with the importance of ducks and fish-eating birds increasing during the fall and late winter. Most prey of resident eagles were taken live or pirated from osprey; scavenging comprised less than 20% of the observed predation. Contamination of the majority of the prey of resident bald eagles was fairly low. However, DDE, PCBs, and mercury were consistently detected at moderate levels and indicated biomagnification in the food-chain. Fish-eating birds in the eagles' diets were apparently the source of elevated environmental contaminants in the eagles on Upper Klamath Lake. Concentrations of DDE in eagle blood and eggs indicated that reproductive success of specific nest sites in the Klamath Basin was reduced. Although contamination was not at levels associated with critical population declines, its effects should not be discounted considering the number and severity of other factors impinging on eagle populations.
Resource Type
Date Available
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Academic Affiliation
Non-Academic Affiliation
Subject
Declaração de direitos
Publisher
Peer Reviewed
Language
Digitization Specifications
  • File scanned at 300 ppi (Monochrome) using ScandAll PRO 1.8.1 on a Fi-6770A in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
Replaces

Relações

Parents:

This work has no parents.

Em Collection:

Itens

Miniatura Título Data de carga Acesso Ações
file details FrenzelRichardW1985.pdf 2017-08-02 Público Baixar