Graduate Thesis Or Dissertation

 

Human impacts on the ecology of bald eagles in interior Alaska 公开 Deposited

可下载的内容

下载PDF文件
https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/m900nz88f

Descriptions

Attribute NameValues
Creator
Abstract
  • To assess the consequences of increased recreational activity on bald eagles (Haliaeetus leucocephalus), we studied factors that influenced their behavior and reproductive success in the Gulkana River basin, Alaska, from 1989 to 1993. Both extrinsic and intrinsic factors were associated with reproductive success. Productivity averaged 0.86 young fledged per occupied territory (SE = 0.05) with 59% nest success (n = 274), but productivity varied among years and subdrainages (P < 0.02). Further, productivity and nest success, but not density, of pairs along the river corridor were negatively associated with levels of human activity (P = 0.037). Pairs that were successful one year were more likely to occupy the same territories, less likely to change nest locations within a territory, more likely to be successful, and fledged more offspring the following year compared to pairs that were previously unsuccessful. Most nesting failure (92%) occurred during incubation. Annual and regional variability in reproductive success of northern bald eagle populations may result from susceptibility to severe spring weather conditions during incubation. Behavior of breeding eagles changed when humans camped near ( 100 m) versus far ( 500 m) from nests (P = 0.0036). Adults decreased the time they fed nestlings and themselves (-30%), preened (-53%), slept (-5 6%) and maintained nests (-50%), but increased the time they brooded nestlings (14%). Further, adults decreased the frequency with which they performed most nesting behaviors, including the amount of prey they consumed at nests (-26%) and fed to nestlings (-29%). Our results show that human activity near nests altered breeding behavior, and suggest that if disturbances in nesting territories were sustained, eagle populations could be affected adversely. The context in which human-eagle encounters occurred affected eagle responses to boating activity. The distance a disturbance was first visible to eagles, the distance they perched from the river, perch height, eagle age, julian date, and ambient temperature were among those factors that influenced both flush response and flush distance of nonbreeding eagles. Breeding adults were less likely to flush and flushed at shorter distances (87.5 ± 10.2 m) than nonbreeding adults (113.0 ± 4.5 in) to approaching boats (P < 0.024). Based on our studies, we recommend a series of strategies to minimize the adverse effects of human activity on breeding and nonbreeding eagles.
Resource Type
Date Available
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Non-Academic Affiliation
Subject
权利声明
Publisher
Peer Reviewed
Language
Digitization Specifications
  • Master files scanned at 600 ppi (256 Grayscale) using Capture Perfect 3.0.82 on a Canon DR-9080C in TIF format. PDF derivative scanned at 300 ppi (256 B&W), using Capture Perfect 3.0.82, on a Canon DR-9080C. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
Replaces

关联

Parents:

This work has no parents.

属于 Collection:

单件