Quadrat Sampling of a Nesting Population of Bald Eagles

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Abstract
An aerial stratified random sample survey of nesting bald eagles (Haliaeetus leucocephalus) was conducted during 1974 on 173,900 km2 of northwestern Ontario and southeastern Manitoba, Canada. Less than the total (target) area was sampled to reduce cost and to avoid a search bias in areas previously visited. Fifty-three 100 km2 quadrats provided estimates of 428 .+-. 158 (37%) eagles, excluding nestlings, and 291 .+-. 88 (30%) breeding areas for the sampled area and 579 .+-. 165 breeding areas for the entire area. Stratification reduced the variance of the means by roughly 22% for breeding areas in the entire area. A real visibility bias requires rigorously standardized techniques and limits the usefulness of estimates of actual numbers. The techniques should be feasible for a larger region and repeated sampling would provide a measure of trends in the status of this eagle species.

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