Groups of two to eight splendid fairywrens remain in their territory and defend it year-round. Territories average in woodland-heath areas; size decreases with increasing density of vegetation and increases with the number of males in the group. The group consists of a socially monogamous pair with one or more male or female helper birds that were hatched in the territory, though they may not necessarily be the offspring of the main pair. Splendid fairywrens are sexually promiscuous, each partner mating with other individuals and even assisting in raising the young from such trysts. Over a third of offspring are the result of an 'extramarital' mating. Helper birds assist in defending the territory and feeding and rearing the young. Birds in a group roost side-by-side in dense cover as well as engaging in mutual preening.