Vocal Behaviour and Annual Cycle of the Western Bowerbird Chlamydera guttata

Abstract

Bowers of the Western Bowerbird Chlamydera guttata were observed at three sites in coastal Western Australia over three years (1977-1980) in order to quantify song output, mimicry and bower attendance and to determine the timetable of events in the birds' life cycle. Tape recordings of vocalisations at bowers were obtained at regular intervals in all months, and a scoring system was used to measure the rate of song output. Data were also obtained on breeding parameters. Bower-owning males were present at bowers all year, and maintained song output through the year with a major peak in September to December. Mimicry followed a similar pattern, with a peak in July to October. The rate of bower visitation also peaked in these months (August to December). Courtship and copulation were observed in August, eggs in August-September, nestlings in October and fledglings in September and October. Clutch size (n=4) and brood size (n=2) were invariably two. After the mating period, while females were nesting, groups of birds (presumably sub-adult males) visited bowers. Display and visitation rates were low from December to the next breeding cycle. Factors inducing mimicry included intrusion by raptors and humans. It is concluded that males advertise the location of new bowers by increased song output, and that mimicry serves partly as a defence mechanism.