Auditory sensitivity in the great tit: perception of signals in the presence and absence of noise.

Absolute and masked auditory thresholds (critical masking ratios) were determined behaviourally in the great tit, Parus major, using a GO/NOGO-procedure. Absolute sensitivity was measured between 0.25 and 10 kHz. In the absence of noise, great tits were most sensitive to frequencies between 2 and 4 kHz. In background noise, however, the sensitivity was only a function of the noise level and was independent of frequency. Critical masking ratios determined for signals between 0.25 and 8 kHz were almost constant (median values varied between 23.8 and 25.9 dB) irrespective of signal frequency. Therefore, in contrast to the majority of bird species, great tits have unusually low critical masking ratios at high frequencies. This means that great tits can use high-frequency vocalizations to communicate efficiently in noisy (i.e. natural) environments. Copyright 1998 The Association for the Study of Animal Behaviour.