Dooling, R.J. and Searcy, M.H. (1981). Amplitude modulation thresholds for the parakeet (Melopsittacus undulatus). Journal of Comparative Psychology, 143, 383-388.

Parakeets were tested for the ability to detect sinusoidal amplitude modulation of broad band noise. Instrumental avoidance conditioning and a psychophysical modified method of limits procedure were used to measure the threshold for detecting amplitude modulation at 10 modulation frequencies between 2 and 2,048 Hz. Below about 40 Hz, modulation threshold is independent of modulation rate and noise level. Above 40 Hz, modulation threshold decreases with modulation frequency at the rate of 3 dB/octave. These results are somewhat different from amplitude modulation functions in humans suggesting different degrees of temporal resolving power in birds and humans. Thresholds for changes in modulation rate re 1-2 orders of magnitude higher than pure tone frequency difference limens.