EFFECTS OF HUMAN ACTIVITY ON BALD EAGLE DISTRIBUTION ON THE NORTHERN CHESAPEAKE BAY

We determined the relationship between bald eagle (Haliaeetus leucocephalus) distribution and human activity on the northern Chesapeake Bay shoreline during 1985-89. Only 55 of 1,117 locations of radio-tagged eagles (4.9%) occurred in the developed land-cover type (greater-than-or-equal-to 4 buildings/4 ha), although 18.2% of potential eagle habitat was developed (chi-2 = 428.9, 4 df, P < 0.001). Eagle use of the shoreline was inversely related to building density (chi-2 = 22.1, P < 0.001) and directly related to the development set-back distance (chi-2 = 5.3, P = 0.02). Few eagles used shoreline segments with boats or pedestrians nearby (P < 0.001). Only 360 of 2,532 segments (14.2%) had neither human activity nor shoreline development. Eagle flush distances because of approaching boats were greater in winter than in summer (xBAR = 264.9 vs. 175.5 m, respectively, P = 0.001), but were similar for adult and immature eagles (xBAR = 203.7 vs. 228.6 m, respectively, P = 0.38). Of 2,472 km of shoreline on the northern Chesapeake, 894 km (36.2%) appears to be too developed to be suitable for eagle use, and an additional 996 km (40.3%) had buildings within 500 m, thereby reducing eagle use. The projected increase in developed land in Maryland (74%) and Virginia (80%) from 1978 to 2020 is likely to determine the future of the bald eagle population on the northern Chesapeake Bay.