A class of chaotic bird calls?

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].