AMPLITUDE REGULATION OF VOCALIZATIONS IN NOISE BY A SONGBIRD, TAENIOPYGIA-GUTTATA

Bird vocalizations are produced under various noise conditions. It cou ld therefore benefit birds to alter the amplitude of their signals as noise conditions change. We tested this by recording male and female z ebra finches, Taeniopygia guttata, as they were subjected to various l evels of white noise. Both sexes increased amplitude levels of vocaliz ation in response to increased levels of noise. Similar results were o btained with humans (the 'Lombard effect'). The results are discussed in terms of the 'active space' of bird song and honest signalling. (C) 1998 The Association for the Study of Animal Behaviour.