Exploratory behaviour modulates the relationship between colony familiarity and helping in a cooperative bird

• We study for the first time whether familiarity modulates the effect of personality on social behaviour in a cooperatively breeding bird.
• We use the novel environmental test to measure exploratory behaviour in the laboratory and intensively monitor social relationships in the Iberian azure-winged magpie.
• We found that familiarity modulates the relationships between social and exploratory behaviour.
• We concluded that familiarity play a role in the value of personality in social tasks for this cooperative breeding species.

Individuals within animal groups may differ in personality and degree of familiarity raising the question of how this influences their social interactions. In Iberian magpies Cyanopica cooki, a portion of first-year males engage in cooperative behaviours and dispersal, allowing addressing this question. In this study, we first investigate the relationship between colony familiarity (native versus foreign) and reproductive status (breeding versus helping) of males during 21 years. Secondly, we measure the exploratory behaviour and monitor reproductive status of a sample of individuals with different colony familiarity during 2 years. Long-term monitoring revealed that foreign individuals were more likely breeders. The analysis on the subset of individuals in which exploratory behaviour was measured revealed a mediatory effect of exploratory behaviour in the association between colony familiarity and helping behaviour. Specifically, among foreign individuals, higher explorative males were more frequently involved in helping behaviour than lower explorative ones. Conversely, among native males, breeders were more explorative than helpers. Our results suggest that aspects of personality may mediate the value of familiarity in reproductive tasks in social species.