Preference for, and spatial arrangement of, decorations of different colours by the Great Bowerbird: Ptilonorhynchus nuchalis nuchalis

摘要

Male bowerbirds (Ptilonorhynchidae) build bowers, and adorn them with decorations to attract mates. We investigated preference for, and spatial arrangement of, decorations of different colours at bowers in a population of the western subspecies of the Great Bowerbird Ptilonorhynchus nuchalis nuchalis, near Darwin, Northern Territory. Decorations mainly comprised snail shells, stones, pieces of glass, and cycad fruits. The colours of most decorations were white, grey or green. Red materials, preferred in eastern populations of the species, were seldom found in these bowers. The spatial distribution of decorations on the bower platforms had a distinct pattern according to colour. Although both grey and white objects were widely spread over the entire platform, the former tended to be placed near the avenue and the latter towards the outer platform. Green objects were consistently placed separately on both sides of the entrances of the avenue. After decorations were experimentally removed from five bowers, the owners placed the decorations of different colours back again in a configuration similar to that present before removal. As green objects were held in the male's bill during courtship displays, their placement next to the avenue entrance was practical for the male, and the background placement of white and grey objects may serve to make green objects and a male's lavender crest more conspicuous.