Nonsimultaneous auditory masking in the budgerigar (Melopsittacus undulatus).

The frequency resolving power of budgerigars and that of humans were compared on several nonsimultaneous masking procedures in which one pure tone is used to mask another. Similar patterns of frequency selectivity were found for all three masking procedures (forward, backward, and combined forward-backward) for both species. Budgerigars showed considerably greater frequency resolving power on all three procedures than humans. Budgerigars also showed differences in frequency resolving power across masking conditions, but human listeners did not. These results indicate that the budgerigar auditory system may be even more highly tuned than was previously thought and suggest fundamental differences between the mechanisms of frequency selectivity of bird and those of humans.