ASSESSING GROUND-BASED COUNTS OF NESTLING BALD EAGLES IN NORTHEASTERNMINNESOTA

We present evidence that the bald eagle (Haliaeetus leucocephalus) pro ductivity survey in the Boundary Waters Canoe Area Wilderness of north eastern Minnesota may have underestimated the number of nestlings duri ng 1986-1988. Recommendations are provided to achieve more accurate gr ound-based counts. By conducting ground-based observations for up to 1 hour/nest, an accurate count of the number of bald eagle nestlings ca n be obtained. If nests are only observed for up to 30 minutes/nest, a n accurate determination of nest success can be made. The effort that managers put into counts should be based on the intended use of the pr oductivity data. If small changes in mean productivity would trigger m anagement action, the less accurate ground-based counts should be cond ucted with caution. Prior to implementing ground-based counts, a study like ours should estimate bias associated with different survey proce dures and the observation time needed to achieve accurate results.