Male great bowerbirds accumulate decorations to reduce the annual costs of signal production

Indicator models of sexual selection suggest that honest mating signals are costly to produce or maintain. Animals that use extended phenotypes as courtship signals may be able to reduce these costs in a given year by reusing nonbodily ornaments acquired during previous years, perhaps affecting signal honesty. I examined whether male great bowerbirds, Ptilonorhynchus nuchalis, are able to reduce the annual costs of signal production by reusing bower decorations acquired during previous years. I paired males that had similar numbers of bower decorations and removed decorations from one member of the pair. Males that had decorations removed from their bowers collected more decorations from the environment the following year than did control males, and they tended to steal more decorations. However, they had fewer decorations at their bowers than did control males, most likely because control males reused almost 50% of the decorations that they had acquired during previous years. These results suggest that individuals that accumulate nonbodily ornaments can reduce the costs of signal production in subsequent years; and that resource accumulation can lead to differences in both behaviour and display quality between individuals that do and do not accumulate resources. I also found a positive correlation between the number of decorations at bowers before removal and the number of decorations acquired by males after removal, suggesting that decoration numbers indicate a maleʹs past condition and present performance.