The Multilevel Society of a Cooperatively Breeding Songbird

Multilevel societies are considered to be the most complex social structures found in vertebrates. They have been observed in primates, cetaceans, ungulates, and elephants but the drivers linked to their emergence as well as the benefits that they offer are not yet clear. However, recent studies have suggested that birds might provide excellent opportunities to fill this theoretical gap. During my PhD, I first described the theoretical link between cooperative breeding and the potential emergence of multilevel societies across Australian and New Zealand bird species. I then analysed non-breeding social networks of cooperatively breeding superb fairy-wrens (Malurus cyaneus) to reveal their structured multilevel society. Using an experimental framework, I demonstrated how individual superb fairy-wrens can adjust cooperative behaviour toward other individuals according to their relative social position in the multilevel society. Further, I showed how cooperative behaviour varies with seasonal changes in environmental condition, and I suggested that the benefits linked to cooperative behaviour are likely to drive the emergence of upper social units in the superb-fairy wren multilevel society during harsh environmental conditions. My research highlights the potential that birds offer to better understand patterns and processes linked to the evolution of multilevel societies and suggests new research avenues in the study of social behaviour of birds.