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

摘要

In many species, males must acquire resources from the environment in order to produce the sexual signalsattractive to females, and indicator models of sexual selection suggest that the costs of resource acquisition may contribute tohonest 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 reusingdecorations acquired in previous breeding seasons. Males reused 240 ± 30 decorations, which represents 30% of thedecorations at their bowers. Males that reused a higher proportion of their decorations were more likely to equal or exceed thenumbers of decorations they displayed at their bowers during the previous breeding season than males that reused a lowerproportion. Males that inherited bower-sites, where they were able to reuse decorations acquired by the previous owner, hadmore decorations than males that built at new sites, where decorations were not available to reuse. Males only reused a highproportion of rocks, a common decoration type, when the distance over which they had to carry the rocks was small, but theyreused less common decoration types regardless of distance. These data suggest there are costs associated with acquiringdecorations, and males reuse decorations to minimise costs.