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ESR 50:167-179 (2023)  -  DOI:

Aerial hearing thresholds and ecoacoustics of a threatened pursuit-diving seabird, the marbled murrelet Brachyramphus marmoratus

Adam B. Smith1,2,*, Michelle Kissling3, Alyssa M. Capuano2, Stephen B. Lewis4, T. Aran Mooney2

1Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense, Denmark
2Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
3Wildlife Biology Program, Department of Ecosystem and Conservation Sciences, W.A. Franke College of Forestry and Conservation, University of Montana, Missoula, MT 59812, USA
4US Fish and Wildlife Service, Division of Migratory Bird Management, Juneau, AK 99801, USA
*Corresponding author:

ABSTRACT: As humans increasingly utilize sensitive coastal areas, diving seabirds like the marbled murrelet Brachyramphus marmoratus face a unique combination of exposure to pervasive anthropogenic sound and acoustically mediated disturbances in terrestrial and marine environments. Despite its threatened status, the sound sensitivities and sensory ecology of this species are unknown, limiting any predictions of the frequencies or sound levels that may induce acoustic impacts. In this study, we measured electrophysiological aerial hearing thresholds for 10 wild individuals captured, sedated, examined inside a field-deployed anechoic chamber and subsequently released. Auditory responses were detected across a 0.5 to 6 kHz frequency range. The median auditory threshold was lowest at 2 kHz (33 dB), while hearing was generally sensitive between 0.75 and 3.8 kHz. B. marmoratus thresholds were elevated compared to other studied alcid species. In-air sensitivities were used to provide an initial prediction of underwater hearing thresholds. To further explore the auditory sensory ecology of this solitary-nesting species, hearing data were also compared to short-term recordings (5 d) of the aerial soundscape of a marbled murrelet nesting habitat. The soundscape contained both abiotic and biotic sounds that contributed to broadband sound levels of 46-55 dB re: 20 µPa rms (0.2-10 kHz). This comparatively quiet habitat enabled relatively frequent detection of anthropogenic sounds within the soundscape. Energy from this acoustic pollution consistently overlapped marbled murrelet sound sensitivities, indicating that the species is susceptible to disturbance from a range of noise types.

KEY WORDS: Hearing · Noise · Soundscape · Seabird · Sensory ecology · Endangered species

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Cite this article as: Smith AB, Kissling M, Capuano AM, Lewis SB, Mooney TA (2023) Aerial hearing thresholds and ecoacoustics of a threatened pursuit-diving seabird, the marbled murrelet Brachyramphus marmoratus. Endang Species Res 50:167-179.

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