Active land planning for long-term Bald Eagle management within the lower Chesapeake Bay (Phase I: Model construction)
Since its elevation to endangered status in 1978, protection of the Bald Eagle and its habitat is governed by the Endangered Species Act. Under this designation, critical habitat is defined as any area essential to the survival and recovery of the species. Current habitat management strategies for nesting Bald Eagles are centered around the protection of active nest trees. Although this practice is essential, it does not address potential nesting habitat. Much habitat remains unoccupied that is both critical to the continued recovery and maintenance of the population and is under imminent risk of development. We quantified 61 topographic, landuse, and disturbance variables within 127 active eagle territories and around 127 randomly chosen points to evaluate their potential as predictors of habitat quality for breeding Bald Eagles. Fifty-four of 61 variables were significantly different between the two samples. Compared to random sites, eagles prefer to nest in areas situated close to large water bodies, away from extensive human disturbance, and having considerable forest cover. A discriminant function analysis was used to determine the linear combination of variables that best differentiate between active and random sites. Sixteen variables conformed to parametric assumptions and were entered into a step-wise discriminant function procedure. The final 4-variable model constructed produced a classification accuracy of 81.5%. In addition to the model variables, 4 distribution constraints were identified within the data set. A combination of these constraints and the 4-variable model were used in the final land classification model.