Title page for ETD etd-5852152749721461


Type of Document Dissertation
Author Berkelman, James
Author's Email Address jberkelman@facstaff.wisc.edu
URN etd-5852152749721461
Title Habitat Requirements and Foraging Ecology of the Madagascar Fish-Eagle
Degree PhD
Department Fisheries and Wildlife Sciences
Advisory Committee
Advisor Name Title
Fraser, James D. Committee Chair
Haas, Carola A. Committee Member
Murphy, Brian R. Committee Member
Ney, John J. Committee Member
Oderwald, Richard G. Committee Member
Stauffer, Dean F. Committee Member
Keywords
  • perch tree
  • madagascar fish-eagle
  • nest tree
  • foraging
  • lake
  • habitat
Date of Defense 1997-05-06
Availability unrestricted
Abstract
With a population estimate of 99 pairs, the

Madagascar fish-eagle (Haliaeetus

vociferoides) is one of the rarest birds of prey in

the world. I investigated the ecological

requirements of the Madagascar fish-eagle in

1994 and 1995 to help determine management

action to prevent its extinction. I investigated

fish-eagle foraging ecology in 1996 to

determine its prey preference and whether fish

abundance and availability affect fish-eagle

foraging rates and foraging success.

Madagascar fish-eagle nest and perch trees

were taller, broader, had more unobstructed

branches, and had a greater arc of accessibility

than unused trees. Perch trees also were

deciduous more often and had a narrower

growth form than unused trees. Nest sites had

more shoreline perch trees than unused sites.

Lakes occupied by fish-eagles were deeper and

clearer, and had more shoreline perch trees,

more fish, a greater total fish weight, and more

fish species than unoccupied lakes.

I developed logistic regression models to

predict the probability of Madagascar fish-eagle

use based on the measured habitat variables.

Nest and perch tree models included tree

height. The nest site model included number of

shoreline perches. Lake models included

number of shoreline perches and either number

of fish, total fish weight, or number of fish

species. These models can be used to predict

fish-eagle habitat use with > 70% accuracy.

Introduced tilapia, Oreochromis spp. and

Tilapia spp., made up the majority of both the

gill net (66.3%) and fish-eagle catch (64.7%) in

similar proportion, which suggests that the

fish-eagle is an opportunistic predator.

Replacement of native fish species by exotics,

thus, probably has not been detrimental to the

island's fish-eagle population. Male fish-eagle

foraging success was positively correlated with

number of fish, total fish weight, and number of

fish species, which suggests that declines in the

fish population could adversely affect the

fish-eagle population.

The results of this study indicate that

Madagascar fish-eagles require bodies of water

with large shoreline trees and an ample fish

population. I recommend greater protection of

aquatic habitats, monitoring and management of

freshwater fish populations, and education of

local people in sustainable tree harvesting

practices.

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