Downing, J.D., Okanoya, K., and Dooling, R.J. (1988). Auditory short-term memory in the budgerigar (Melopsittacus undulatus). Animal Learning and Behavior, 16, 153-156.

We trained two budgerigars (Melopsittacus undulatus) with operant techniques in a delayed matching-to-sample task using pairs of acoustic stimuli. These stimuli included simple pure tones, complex, species-specific vocalizations, and tone-vocalization combinations. The birds were then tested with different retention intervals. The budgerigars' short-term memory was similar for complex, species-specific vocalizations and for simple pure tones. By contrast, they showed significantly better short-term memory when tested with two sounds drawn from different acoustic categories.