Fig. 5

The evolution of the skrraa call mapped above a simplified phylogenetic tree for the bowerbirds (adapted and modified from Borgia and Coleman 2000). The presence (+) or absence (−) of the skrraa call in aggressive and courtship interactions is mapped above the tree. This example clearly shows when the call was co-opted from its context in male–male aggression to serve a new function in male–female communication during courtship. Triangles at the end of branches indicate a larger, monophyletic group. The spotted group represents five species (in the genus Chlamydera), all of whom use the skrraa call in both aggressive and courtships contexts