Intensity discrimination as a function of level and frequency in three species of birds

Abstract

Many studies have examined frequency discrimination in birds, but there has not been as complete a description of avian intensity discrimination abilities. Birds appear to be slightly less sensitive to changes in intensity than humans and other mammals; however, few studies have systematically looked at the effects of both frequency and presentation level on intensity discrimination in birds. Here we describe intensity discrimination as a function of frequency and sensation level in two small songbird species, the canary (Serinus canarius), the zebra finch (Taeniopygia guttata), and a nonsongbird species, the budgerigar (Melopsittacus undulatus). Intensity difference limens (DLIs) for pure tones were obtained from birds using standard operant conditioning procedures and the Method of Constant Stimuli. DLIs ranged from approximately 2–6 dB, which are slightly larger than the DLIs reported in mammals. For all three species, DLIs become smaller with increasing presentation level, but show little effect across frequency for a given level. These results are consistent with previous reports in other species. [Work supported by NIH DC01372 to RJD and DC05450 to AML.]