Male Great Bowerbirds perform courtship display using a novel structure that rivals cannot destroy

Male–male competition can cause less competitive males to pursue alternative mating strategies or defer reproduction until they are older. For species that display using non-bodily ornaments, male interference can also involve limiting rivals’ access to display materials. I document a novel solution to male interference with external display structures in Great Bowerbirds (Ptilonorhynchus nuchalis). Males build and display at stick structures (‘bowers’), but they frequently destroy other males’ bowers. I show that some males, including young individuals, adapt to this interference by displaying around tree trunks instead of bowers. Tree trunks cannot be destroyed, so males can display at them despite interference. Display rates were higher at tree trunk display sites (‘display trees’) than bowers. Display trees had a basal diameter similar to the width of the front of the bower walls, allowing males to display in a similar manner as at bowers. Bower-owning males stole more experimentally placed decorations from display trees than random trees or bowers; most attempts at bower building by males at display trees were destroyed. Display trees were located closer to bowers than bowers were to each other. Display trees may allow younger and less competitive males to attempt to attract females visiting nearby established bowers and to gain competence in display.