Bald eagles (Haliaeetus leucocephalus) monitor their immediate acoustic environment vigilantly

Abstract

As part of an initial effort to determine if acoustic signals can be used to discourage eagles from entering wind turbine facility airspaces and thereby reduce morbidity/mortality collision rates, behavioral responses of bald eagles (Haliaeetus leucocephalus) to a battery of both natural and synthetic acoustic stimuli of varying spectral complexities were studied. Each signal was directed randomly to one of two loudspeakers in a sequence of ~10 trials, and the stimulus order was randomized for each bird. A variant of an observer-based psychoacoustic protocol was implemented, and judges were instructed to report the absence or presence of a response, response strength, and other distinctive response attributes. In pilot studies, subjects responded to ~74% of trials across all stimuli. Responsivity was greater to spectrally complex stimuli (~80% vs 59%), and greater responsivity was observed to natural stimuli than to synthetic stimuli (~82% vs 69%). Responsive subjects oriented correctly in the direction of the signal source in ~74% of trials. A significant difference in overall responsivity was not observed across stimulus sets, although habituation was observed across repeated trials when responses to all stimulus types were combined. The relevance of findings in relation to the design of deterrence/alerting protocols will be discussed. [Work supported by DOE Grant No. DE-EE0007881.] As part of an initial effort to determine if acoustic signals can be used to discourage eagles from entering wind turbine facility airspaces and thereby reduce morbidity/mortality collision rates, behavioral responses of bald eagles (Haliaeetus leucocephalus) to a battery of both natural and synthetic acoustic stimuli of varying spectral complexities were studied. Each signal was directed randomly to one of two loudspeakers in a sequence of ~10 trials, and the stimulus order was randomized for each bird. A variant of an observer-based psychoacoustic protocol was implemented, and judges were instructed to report the absence or presence of a response, response strength, and other distinctive response attributes. In pilot studies, subjects responded to ~74% of trials across all stimuli. Responsivity was greater to spectrally complex stimuli (~80% vs 59%), and greater responsivity was observed to natural stimuli than to synthetic stimuli (~82% vs 69%). Responsive subjects oriented correctly in the direction ...