Female assortment in Gouldian Finch ( Chloebia gouldiae ) Flocks: A case of female-driven social niche construction?

The organization of animal groups is both a cause of and a consequence of patterns of interactions among individuals. The stability of social organization reflects how individuals construct and maintain resilient patterns of interactions across changes in group size and membership. Who you choose to associate with may have numerous advantages, primarily through avoiding potentially costly interactions with others. In this study, we describe patterns of social interactions in multiple flocks of Gouldian finches that were exposed to changing social conditions. In the first condition, flocks experienced repeated introductions of juveniles into the group. In a second condition, an adult flock was exposed to changing conditions where males were swapped between the flocks. In almost all flocks, we found significant levels of female-driven sex assortment. Further analysis shows that females were more likely to “leave” interactions after being approached by males than males, thus constituting a social decision to avoid male interactions. These findings highlight how the stable interactive decisions made by individuals contribute to higher-order patterns of organization in bird flocks.