Evidence is presented that the basic vocalized sound produced by some cocka
toos, specifically the Australian sulfur-crested cockatoo (Cacatua galerita
) and the gang-gang cockatoo (Callocephalon fimbriatum), has a chaotic acou
stic structure rather than the harmonic structure characteristic of most bi
rdsongs. These findings support those of Fee et al. [Nature (London) 395(3)
, 67-71 (1999)] on nonlinear period-doubling transitions in the song of the
zebra finch (Taeniopygia guttata). It is suggested that syllables with cha
otic structure may be a feature of the songs of many birds. (C) 2000 Acoust
ical Society of America. [S0001-4966(00)04108-4].