Using birds to examine assumptions about the evolution of song, aggression and bright colours. Buried in our understanding of evolution and animal behaviour are many entrenched assumptions. Most of these assumptions never been explicitly tested. I use birds to test some of these assumptions and along the way I have found some surprising answers. I’ll present some of this research, with particular focus on what it makes a good female, the evolution of song and vocal learning, and the costs of bright plumage. These studies included research on sparrows in N America, fairy-wrens and finches in Australia, and pukeko and titipounamu (rifleman) in New Zealand.