Disturbance because of human activity, including recreation on wildlands, can affect bird behavior which in turn can reduce breeding success, an important consideration for species of management concern. We observed Golden Eagles (Aquila chysaetos) during the breeding season to determine whether the probability of flushing was affected by the type of recreationist, distance to encounter, eagle nest attendance, or date. We monitored eagles in 23 nesting territories from distant (600-1,200 m) observation points and recorded recreation activity within 1,200 m of eagles in the Owyhee Front of southwestern Idaho. In most (86%, n = 270) encounters, eagles did not flush in response to recreationists; however, whether an eagle flushed was affected by the type of recreationist and whether an eagle was at or away from the nest. Eagles were 60 times more likely to flush in response to recreationists that stopped a motor vehicle and transitioned to walking (11 of 17 passes) and 4.5 times more likely to flush in response to off-road vehicle (ORV) riders (17 of 121 passes) than during encounters with road vehicles (7 of 107 passes). Flushing was 12 times more likely for eagles away from nests (23 of 87 passes) than eagles at nests (13 of 183 passes). Eagles flushed at greater distances in response to recreationists that transitioned from motor vehicles to walking (lsmean = 620 m) than when responding to either ORV riders (lsmean = 525 m) or road vehicles (lsmean = 318 m). Flushing distances tended to decline throughout the breeding season to suggest seasonal changes in the costs and benefits of responding to disturbance. After flushing from nests, most eagles (77%) spentaway, but some (23%) spent >90 mins away from nests. Limiting recreational activities within 650 m and 1,000 m of nest sites may decrease nest-site flushing events by 77% and 100%, respectively. Because eagles seem most sensitive to humans transitioning between motorized and non-motorized recreation, land managers may strike a balance between access needs of recreationists and buffering eagles from disturbance by using a mix of trail closures and no-stopping zones that prevent transitions from motorized to walking activities.
This document was originally published in Wilson Journal of Ornithology by Wilson Ornithological Society. Copyright restrictions may apply. doi: 10.1676/16-165.1
Spaul, Robert J. and Heath, Julie A.. (2017). "Flushing Responses of Golden Eagles (Aquila chrysaetos) in Response to Recreation". Wilson Journal of Ornithology, 129(4), 834-845.