Dooling, R.J.  and Saunders, J.C. (1974). Discrimination of the intensities of tones by the parakeet (Melopsittacus undulatus). J. Acoust. Soc. Am. 56, S39.

Using avoidance conditioning and a modified method of limits, we measured the intensity difference limens of three parakeets at six sensation levels of a 2.86-kHz tone. At sensation levels above 50 dB, the average value of the relative difference limen is about 3.0 dB. Below a sensation level of 50 dB, the relative difference limen increases as the intensity of the tone is decreased. Intensity difference limens for the parakeet are 2–3 dB larger than similar measures for man and other mammals and suggest that the avian ear may not be as sensitive to intensity changes as are the ears of many mammals. [Supported by NIH Grant No. NS 03856 to the Central Institute for the Deaf.]