Birds with small brains but complex societies

Being called a bird brain might not be such a bad thing…

Animal behaviour experts used to believe that only large-brained mammals could form complex social structures - but a recent study shows that the vulturine guineafowl, a bird native to West Africa, can do so too.

Although many species form groups, the vulturine guineafowl is special because multiple distinct groups of birds form part of an interacting society. The groups are tight-knit, their memberships stay the same, and each group has a preference for which other groups to interact with.

Lead author Danai Papageorgiou, at the Max Planck Institute of Animal Behaviour in Germany, explained that “the guineafowl maintain stable membership within the groups. These groups associate preferentially with others and then they split back into their original groups.”

This study looked at 400 vulturine guineafowls living in a savannah in the Mpala Research Centre in Kenya. The birds formed 18 groups and they tracked them using colour tags and GPS for a year.

Papageorgiou and her group established how independent the groups of birds were from each other through ‘social network analysis’, which uses information about how close the tracked individuals were from each other over time, to characterise the guineafowl social network.

Papageorgiou said that members of the same group stayed relatively close to each other, but that the different groups interacted peacefully. “In the wet season, which is the breeding season for the vulturine guineafowl, several different groups come together and aggregate in glades. When the weather is dry, different groups come together and travel to water resources.”

Besides the guineafowl forming well-defined groups within their larger society, within each group there is also a social structure that depends on the dominant status of the individuals. “Aggression is quite rare in the species between groups, but sometimes it happens and we don’t think it’s so much about food resources, but mostly about maintaining group membership and status”, said Papageorgiou.

But although there is clear evidence of dominance of some individuals over others, the vulturine guineafowl seem to make collective decisions democratically. “There is nothing like despotism. Decisions are shared among individuals” said Papageorgiou. Any of the birds can initiate a collective action and be involved in the decision-making process. However, “the exact mechanisms under which decisions are taken depend mostly on the context.”

The take-home message is that the capacity for forming multi-level societies is not as special a trait as we think. The social structures of other organisms have been understudied, and it is possible that other species form complex societies too.