The great tit's (Parus major) auditory resolution in azimuth

Abstract

1. Two male great tits (Parus major) were trained to distinguish between sounds from two locations in an operant two alternative, forced choice procedure with positive reinforcement. 2. The angle between the two sound sources, as experienced from the position of the experimental subject, was varied. The angle at which the birds scored 65% correct responses in 60 choices (which corresponds toP = 0.03, two-tailed, binomial test) was defined as the minimum resolvable angle (MRA). 3. The resolution in azimuth for four natural vocalizations, the ‘seeet’ alarm call, the ‘scolding’ call, the mobbing call, and a song element, was 45°, 16°, 20°, and 18°, respectively (Fig. 2). The MRAs correlated well with the results from artificial stimuli with a comparable frequency. 4. MRAs for 300 ms sine wave stimuli were determined from 500 Hz to 8 kHz: The u-shaped function relating MRA with frequency had a minimum at 2 kHz, with a best MRA of 20°. At 500 Hz and 8 kHz the MRAs were 66.5° and 52°, respectively. MRA of a 300 ms white noise stimulus was 20.5° (Fig. 3). 5. The duration of the stimulus had no effect on the resolution in azimuth for a range of durations from 40 ms to 300 ms (Table 1). This suggests that the great tit may locate a sound source in an open loop fashion.