Dooling, R.J., Walsh, J.K., and Tepas, D.I. (1975). Auditory evoked brain responses from the parakeet: Intensity functions. Physiological Psychology, 3, 307-311.

Averaged auditory evoked brain responses were collected from the skulls of unanesthetized parakeets. These responses were collected at eight intensities of a 1,000-Hz tone. The waveform of the evoked response was highly consistent across birds, with a major positive deflection occurring at about 20 msec after tone onset, followed by a negative deflection at about 40 msec and a second positive deflection at about 100 msec. Over the intensity range examined, there is a log-linear relation between the intensity of the stimulating tone and the size of the evoked response. Threshold estimates obtained from this evoked response data compare favorably with the behavioral threshold at 1,000 Hz for the parakeet.