Hormonal governance of social behaviour in Siberian jays (Perisoreus infaustus)

Social behaviour in animals arises from a continuous dialogue between environmental conditions, social contexts, and internal physiological states. Yet, how hormones shape social interactions under natural conditions remains poorly understood, especially in birds. In my doctoral research, I investigated the role of oxytocin — a neuropeptide known for mediating social bonding in mammals — in a wild population of Siberian jays, a socially complex corvid inhabiting the boreal forests of northern Scandinavia.

I developed the first minimally invasive field protocol to measure oxytocin in free-living passerines, enabling repeated hormone sampling without disrupting their natural behaviour. Using this method, I found that individuals with higher oxytocin levels were more likely to initiate affiliative contact with group members, providing the first evidence that endogenous oxytocin variation promotes prosociality in wild birds. However, experimental elevation of oxytocin did not alter behaviour, highlighting a nuanced hormonal regulation likely adapted to the jays’ stable social structure.

This work establishes a foundation for field endocrinology of sociality in birds and shows that the evolutionary conservation of oxytocin lies not in its uniform function, but in its ecological flexibility — fine-tuning social interactions to the dynamics of natural life.