Frequency discrimination in budgerigars (Melopsittacus undulatus): effects of tone duration and tonal context

Studies of frequency resolving power in budgerigars (Melopsittacus undulatus) have shown that this species has excellent discrimination abilities for both simple and complex sounds falling in the region of 2 to 4 kHz--the frequency range of their contact call. In four experiments, frequency discrimination by budgerigars of short tones similar to elements found in the contact call was examined. Frequency difference limens (FDLs) for simple pure tones at 2.86 kHz were constant for tone durations above 20 ms but higher for shorter tones. Budgerigars generally showed larger FDLs for shorter duration 1-, 2-, and 4-kHz pure tones. FDLs in budgerigars for 20-ms tones embedded in a sequence of six other tones were similar to FDLs measured for tones of the same frequency presented in isolation. Moreover, there was no effect of introducing trial-by-trial variation in the location of the frequency change in the seven-tone complexes for budgerigars, a condition for which humans showed a large decrement in performance. Taken together, these results suggest budgerigars possess enhanced spectral resolving power for short duration pure tones when they are embedded in contact call-like tonal patterns.