Lake selection by Madagascar Fish-Eagles

Abstract

We investigated fish abundance and habitat characteristics at 32 lakes occupied by Madagascar Fish-Eagles (Haliaeetus vociferoides) and 32 randomly selected unoccupied lakes between Morondava and Boriziny in western Madagascar from May to November 1995. We measured lake and shoreline habitat characteristics and used gill nets to sample fish populations. Compared with unoccupied lakes, lakes occupied by fish-eagles were deeper and clearer, had more shoreline perch trees, and yielded gill-net catches with more fish, a higher total fish mass, and more fish species. A logistic regression model with number of shoreline perch trees and number of fish species caught in gill nets as independent variables correctly classified fish-eagle use for 76.6% of the lakes in the study. A model with number of shoreline perch trees alone was 71.9% accurate, suggesting that perch-tree availability is the most important factor limiting populations of Madagascar Fish-Eagles. The results indicate that Madagascar Fish-Eagles require bodies of water with large shoreline trees and ample populations of fish.