Stalk-eyed flies

success because in this highly competitive business, many males’ bowers are rarely visited by females. The researchers assessed the quality of the bowers in terms of the density and thickness of the sticks used in its construction and also its symmetry. They also checked the decorations on display and grouped them into five categories: artificial and yellow, brown, blue and white natural. The behaviours recorded included: visits by females to the bowers; copulations; singing and dancing displays by the owner to females; `solitary’ displays by the owner when no other bird was in the camera’s field; bower painting by the owner, during which the male coated the inside of the avenue with a masticated mix of saliva and hoop pine leaves and stealing of decorations and/or destruction of the bower by rival males. What the researchers found was that the females appear to go through a two-stage process using different signals. Females preferred to take a peek at the bowers of larger males and those with the higher rates of solitary displays. The showy decorations appeared to influence visits to a lesser extent. The females showed some preference for visiting bowers with blue and white natural decorations and tended to avoid those displaying more natural yellow decorations. After controlling for female visitation rates, mating success of males was still related to their size but the decorations now appear to play second fiddle to the male’s painting activities. The researchers noted that the females were often seen to nibble at the paint daubed on the bower sticks, which suggested it might provide a chemical signal, something highly unusual in birds. The authors believe that mate choice in satin bowerbirds is an ideal subject for the study of the evolution of multiple signals. Magazine R533