Stealing behavior and the maintenance of a visual display in the satin bowerbird

Honest signals that indicate male quality have been observedin many species and are thought to have evolved to allow malesto assess rivals accurately and respond to "cheaters." Femalescould potentially also use the same honest signals as reliableindicators of male quality. In bowerbirds, the numbers of specificbower decorations may serve as an honest signal of male quality:this study investigates whether decoration stealing among malesatin bowerbirds at the Bunya Mountains, Australia, may alsoinvolve honest signals. In this study, we aimed to determine1) predictors for the degree to which individual male satinbowerbirds steal, and are stolen from, and 2) predictors forwhy some male pairs interact by stealing, whereas other pairsdo not. We also assessed how experimentally standardizing thenumber of decorations on bowers would affect the 1) frequencyof stealing, 2) specific interactions among males, and 3) distributionof decorations across bowers. Bower decorations were labeledand tracked through one breeding season. Males that were successfulstealers, stole from other successful stealers, had many feathersand bottle tops on their bowers and painted their bower wallsoften. Male pairs were more likely to interact by stealing iftheir bowers were in close proximity. Most of the stealing observedwas of a reciprocal nature. After we standardized the numbersand types of decorations on a small group of males' bowers,the mean number of daily stealing gains and the total numberof males interacting by stealing did not change. In addition,no significant novel stealing interactions were initiated afterthe manipulation. The average number of all bower decorationsand the average number of rosella feathers on a given male'sbower prior to the manipulation were proportional to the averagenumbers for the period after the manipulation. Furthermore,males that originally had better collections of decorationstended to suffer fewer losses due to stealing after the manipulation.Our results suggest that the total number of decorations, thetotal number of rosella feathers on a male's bower, and possiblystealing behavior, may form part of the basis of an honest signalindicating male quality and therefore might be correlated withmating success.