Aspects of frequency discrimination in passerine birds and pigeons

Used a positive reinforcement technique to measure pulsed-tone, frequency difference limens (DLs) in 7 redwing blackbirds (Agelaius phoeniceus) and 7 brown-headed cowbirds (Molothrus ater). Direct comparisons were made with 2 nonpasserine control pigeons and the 1st author. Blackbirds were more sensitive than pigeons to frequency changes above 1.0 kHz but less sensitive below 1.0 kHz. DLs in all Ss were within the range of nonhuman mammals but higher than those of humans. The lowest differential frequency sensitivity/standard frequency (Δf/f) ratio for all Ss occurred at 4.0 kHz, a frequency for which they exhibit minimal absolute auditory thresholds and which is a dominant component in the redwing song. As in humans, blackbird sensitivity at 1.0 and 2.0 kHz declined as sensation level (SL) was decreased, but at 4.0 kHz, sensitivity had no clear dependence on SL. At 8.0 kHz, blackbird sensitivity increased with a decrease in SL. This latter frequency is a dominant component in the cowbird song. Differences in frequency sensitivity were also found as a function of the direction of frequency shift from the standard: Upward shifts produced lower DLs at 1.0 and 2.0 kHz, and downward shifts produced lower DLs at 8.0 kHz. (35 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved).