Auditory sensitivity of the redwing Blackbird (Agelaius phoeniceus) and brown-headed cowbird (Molothrus ater)..

Abstract

Auditory sensitivity of redwing blackbirds and brown-headed cowbirds was measured with 3 behavioral procedures. In the 1st, a go-left-go-right procedure, a bird initiated a trial by pecking a center key; a tone was presented with 50% probability on each trial. A bird was rewarded with grain for pecking a right or left key, depending on whether a tone was present or not. In the 2nd, a go-no-go procedure, a bird pecked the center key continuously until a 2-s tone sounded; reinforcement then occurred if the bird pecked the right-side key during the tone. In the 3rd, a modified go-no-go procedure, clearly audible tones were inserted into the regular go-no-go procedure whenever near-threshold tones were missed. All procedures produced similar thresholds for both redwings and cowbirds; hearing encompassed the range from 125 Hz to 10 kHz, with lowest thresholds of 4-20 dB (SPL [sound pressure level]) in the 2-4 kHz range. Two pigeon control subjects gave stable thresholds only under the modified go-no-go procedure.