The Effect of Sunlight on Decoration Placement and Mating Success in Male Satin Bowerbirds

Title of Document: THE EFFECT OF SUNLIGHT ON DECORATION PLACEMENT AND MATING SUCCESS IN MALE SATIN BOWERBIRDS Archer Freni Larned, Master of Science 2012 Directed By: Dr. Gerald Borgia, Professor, Department of Biology Males of some bird species choose sunlit display sites to enhance their visual signal. Satin bowerbird (Ptilonorhynchus violaceus) males place colored decorations on their bower platform as part of their courtship display. Little is known about how illumination affects the attractiveness of decorations. We analyzed photographs to quantify the amount of direct illumination on the bower and the number of blue decorations in sunlight. We found that the proportion of sunlight on the entire bower platform during peak female visitation periods is correlated with male mating success. The North platform, where decorations are concentrated, was proportionately more illuminated than the South platform. Males placed decorations in more sunlit areas on the platform and returned moved blue decorations to their original locations, suggesting that males actively place blue decorations in sunlit areas. This is the first study to demonstrate that greater illumination in off-body displays may be important for attracting females. THE EFFECT OF SUNLIGHT ON DECORATION PLACEMENT AND MATING SUCCESS IN MALE SATIN BOWERBIRDS