Preferences for coloured bower decorations can be explained in a nonsexual context

The sensory bias model of sexual selection suggests that elaborate male secondary sexual traits evolved to exploit biases in the female's sensory system. Such biases may have evolved in a nonsexual context. Male bowerbirds build and decorate elaborate structures, bowers, which function as targets of female choice. The colour of decorations used on bowers appears to be important in determining a male's mating success. We tested two predictions made by the sensory bias model, using cache presentation experiments of artificially coloured grapes made to captive bowerbirds of five species. We first searched for evidence of ancestral biases for certain colours that could explain current colour preferences across species. We found no single parsimonious explanation for ancestral patterns of colour preference across the family. We next tested whether female preference patterns could be explained in a nonsexual, foraging, context. For both of the species where sufficient data could be collected, female foraging preferences for grapes were significantly related to male preferences for grapes used as bower decorations. Our results suggest that choice of bower decoration colour may have evolved to exploit a bias in the female's sensory system, originally shaped by selection on foraging practices. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.