Flushing responses of wintering bald eagles to military activity

We studied flushing responses of wintering bald eagles (Haliaeetus leucocephalus) to military firing activity, helicopter overflights, and boating on the Nisqually River and Muck Creek on the Fort Lewis Army Reservation, Washington, during 1991-94. Eight percent of 1,452 eagles monitored near Muck Creek Bushed during 373 firing events; 45% from ordnance explosions, 9% from automatic weapons fire, 6% from artillery impacts, 4% from mortar impacts, and 3% from small arms fire. Flushing by eagles decreased with increasing distance from firing events (16% flushed at 0.5-1.0 km, 9% at 1-2 km, 4% at 2-4 km, and < 1% at 4-6 km). Forty-seven percent of 919 eagles Bushed in response to 48 helicopter overflights, 37% on the Nisqually River and 53% on Muck Creek. Sixty-one percent of 1,825 eagles Bushed in response to 52 experimental boat disturbances on the Nisqually River. Subadults Bushed more often than adults, and eagles feeding or standing on the ground flushed more often than those perching in trees. Our data suggest that ordnance explosions, low-level helicopter overflights, and boating should be restricted near eagle foraging areas.