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