Little is known about how animal personality affects social interactions and what the fitness consequences are. This is especially relevant in highly social species like cooperative breeders, where individuals interact frequently, often with close relatives. Under such circumstances reducing conflict and competition can increase fitness. This can be achieved through social niche specialisation, where individuals perform specific functions within their social unit, likely related to individual personality traits. To test this we related individual exploration scores obtained from a novel environment test (a measure of coping with stress) to brood care behaviour in a wild population of superb fairy-wrens (Malurus cyaneus). Exploration scores of breeders and helpers were compared to nestling provisioning rates and nest defence from a conspecific ‘intruder’ (taxidermic mount). To test for broader niche specialisation, individuals’ feeding rates and nest defence were also compared. Females provisioned nestlings at a relatively higher rate than males, but provisioning was not related to exploration score in general or within role (breeder/helper) or sexes. During nest defence, birds approached the ‘intruder’ significantly closer and stayed near it for longer when other group members were present. Males in groups with helpers showed a positive relationship between time spent near the model and exploration score, whereas females in those groups and breeders without helpers showed no such relationship. Finally, relative feeding rate was not related to nest defence intensity. Thus, group living may provide fitness benefits in two ways: (i) the presence of group members stimulates nest defence, (ii) personality variation can promote social niche specialisation: while more exploratory birds defend, less exploratory birds can keep feeding. This may lead to reduced disturbance at the nest and a more constant feeding rate, benefiting nestling development.