Experimental evidence of local variation in the colour preferences of Great Bowerbirds for bower decorations

Abstract

Previous observational studies near Darwin, Northern Territory, revealed that males of a population of the western subspecies of the Great Bowerbird (Ptilonorhynchus nuchalis nuchalis) gathered only green objects as coloured decorations for their bowers. To test whether collection of certain coloured objects by Bowerbirds was caused by the skew of availability of such colours in the environment, we conducted experiments in which glasses of various colours were placed in or near bowers. We supplied shards of coloured glass of five colours (Brown, Yellow-Green, Green, Dark Olive-Green and Dark Blue) and painted glass of six colours (Red, Yellow, Light Green, Deep Green, Light Blue and Blue). Both Green and Deep Green were favoured, whereas other colours were ignored or disfavoured, especially Red and Yellow. Males in our population showed a narrow range of colour preferences even when a wide choice of colours was available, which differs from findings for the eastern subspecies (P. n. orientalis), in which red and purple were favoured. Green objects were placed beside the avenue entrance, probably for ready access when displaying to females in the avenue. We suggest that the green was preferred because it contrasts with the lilac nuchal crest displayed to females during courtship.