April 1995
·
64 Reads
·
34 Citations
Journal of Wildlife Management
We studied the influence of shoreline perch trees and human development on bald eagle (Haliaeetus leucocephalus) distribution on the northern Chesapeake Bay. Bald eagle distributions may be determined by available suitable shoreline perch areas. Models based on human development and shoreline habitat variables may alleviate problems associated with classifying bald eagle habitat by identifying characteristics predictive of eagle presence. We observed 2,962 eagles during 36 shoreline surveys and relocated 110 radio-marked eagles 1,350 times during 1985-92. We counted 5,928 suitable (height ≥6.1 m, diam at breast height [dbh] ≥20.0 cm, and shoreline accessibility ≥30°) perch trees in 229, 250- × 50-m segments along shoreline during 1990-91. Shoreline segments used by eagles had more suitable perch trees (x̄ = 30.3 vs. 22.0; P < 0.001) and a larger percentage of forest cover (x̄ = 54.9 vs. 39.4; P < 0.001) than unused segments. Suitable trees on segments with eagle use were closer to water than suitable trees on segments without eagle use (x̄ = 8.4 vs. 17.0 m; P = 0.009). Most segments classified as marsh (66.7%) were unused. Marsh segments had fewer suitable perch trees, less forest cover, and a greater mean distance from water to the nearest suitable perch tree than did other land types (P < 0.001). Developed segments had fewer suitable perch trees, less forest cover, and a shorter distance from water to the nearest suitable perch tree than undeveloped forested segments (P ≤ 0.01). Logistic regression models based on various measures of perch tree abundance and shoreline development correctly predicted eagle use for 65.9-71.0% of segments.