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Sibling Rivalries Lead to Friendly Finches

A new study has revealed that growing up with lots of siblings – and fighting over food – makes zebra finches more sociable in later life. In contrast, finches with fewer siblings become pickier about who they hang out with, and are less outgoing.

The study, published in Proceedings of the Royal Society B (, looked at zebra finches in the wild near Broken Hill, and found that their family size early in life was a key factor determining how gregarious the birds became. The researchers attribute this difference to the amount of stress the juvenile birds experienced competing for food with their siblings.

Zebra finches tend to form lifelong breeding pairs and co-parent their offspring, sharing the foraging duties. This means the family unit has a strong impact on the birds’ upbringing.

Being friendlier and less choosy about social groups can lead to improved survival rates for the finches and their offspring as they escaped the family and became independent more quickly. Finches from big families were happy to switch between different social groups and forage with many others, thus becoming better-connected in the social network.

Prof Simon Griffith of Macquarie University’s Department of Biological Sciences said the findings suggest that an individual’s sociability is set early in life. “This study explains why there is variation in how social these birds are. Sociability is an important aspect of an individual’s personality and can shape its ability to gain resources and mates throughout its life,” he said.

“While we can’t yet explain why stress in early life leads to more sociability, this study builds on the evidence that early developmental conditions determine social behaviour and social structures.”