Do male Great Bowerbirds (Ptilonorhynchus nuchalis) minimise the costs of acquiring bower decorations by reusing decorations acquired in previous breeding seasons?

Abstract

In many species, males must acquire resources from the environment in order to produce the sexual signals attractive to females, and indicator models of sexual selection suggest that the costs of resource acquisition may contribute to honest sexual signalling. I used data collected during a 5-year field study of the Great Bowerbird (Ptilonorhynchus nuchalis) to test the hypothesis that acquiring decorations is costly to males in time and energy, and that males minimise costs by reusing decorations acquired in previous breeding seasons. Males reused 240 ± 30 decorations, which represents 30% of the decorations at their bowers. Males that reused a higher proportion of their decorations were more likely to equal or exceed the numbers of decorations they displayed at their bowers during the previous breeding season than males that reused a lower proportion. Males that inherited bower-sites, where they were able to reuse decorations acquired by the previous owner, had more decorations than males that built at new sites, where decorations were not available to reuse. Males only reused a high proportion of rocks, a common decoration type, when the distance over which they had to carry the rocks was small, but they reused less common decoration types regardless of distance. These data suggest there are costs associated with acquiring decorations, and males reuse decorations to minimise costs.