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Frequency sensitivity in Northern saw-whet owls (Aegolius acadicus)
Julia R Beatini1, Glenn A Proudfoot1, Megan D Gall2
1Biology Department, Vassar College, 124 Raymond Ave, Poughkeepsie, NY, 12604, USA.
Summary
Northern saw-whet owls possess a broad hearing range, crucial for acoustic prey localization. Their exceptional auditory sensitivity is likely shaped by ecological factors rather than their own vocalizations.
Area of Science:
- Bioacoustics
- Auditory Neuroscience
- Avian Ecology
Background:
- Northern saw-whet owls (Aegolius acadicus) have unique asymmetrical ears aiding acoustic prey localization.
- Limited research exists on the auditory capabilities of this owl species.
- Understanding auditory sensitivity is key to evolutionary biology and ecological interactions.
Purpose of the Study:
- To assess auditory sensitivity in Northern saw-whet owls using auditory brainstem responses (ABRs).
- To test hypotheses on the evolution of auditory sensitivity: sender-receiver matching, ecological constraints, and phylogenetic/morphological constraints.
Main Methods:
- Evoked auditory brainstem responses (ABRs) using tonebursts.
- Analysis of ABR amplitude, latency, and threshold.
- Comparison with audiograms of other owl species, including Eastern screech-owls (Megascops asio).
Main Results:
- Hearing range determined to be 0.7 to 8.6 kHz, with peak sensitivity between 1.6 and 7.1 kHz.
- Audiogram shape is similar to other owl species, suggesting phylogenetic or morphological constraints.
- Lower ABR thresholds (10-25 dB lower than Eastern screech-owls) indicate heightened absolute sensitivity, particularly at frequencies outside conspecific vocalizations.
Conclusions:
- Phylogeny or morphology likely constrains the overall frequency range of auditory sensitivity in owls.
- Exceptional low-frequency sensitivity in Northern saw-whet owls suggests adaptation to ecological factors (e.g., prey sounds) rather than solely conspecific communication.
- This study provides critical data on avian auditory systems and their evolutionary drivers.
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