Testing auditory sensitivity in the great cormorant (Phalacrocorax carbo sinensis): Psychophysics vs. Auditory brainstem response

Psychoacoustic and electrophysiological methods were used to measure the in-air hearing sensitivity of the great cormorant (Phalacrocorax carbo sinensis). One individual was used to determine the behavioral thresholds, which was then compared to previously collected data on the auditory brainstem response (ABR) thresholds from 11 individuals. The behavioral hearing sensitivities were measured at 500 Hz, 1 kHz, 2 kHz, 4 kHz, and 6 kHz, while the ABR hearing sensitivities were measured at 500 Hz, 1 kHz, 2 kHz, and 6 kHz. For both methods the sensitivities were found to be lowest at 2 kHz. The ABR hearing thresholds were found to be 23-53 dB higher than the hearing thresholds determined from the psychoacoustic results, but the audiograms derived with the two methods shared similarities in shape. The results from this study show that the hearing sensitivities of the great cormorant are more sensitive in the behavioral results than from the ABR measurements.