The number of strong social bonds is linked to survival in a cooperative bird

Recent evidence, particularly from mammals, shows that variation in the quality of social relationships is associated with survival. In parallel, studies across diverse taxa have reported consistent individual differences in social network traits over time. However, few studies have assessed whether the specific social traits associated with survival are also repeatable within individuals, limiting our understanding of their contribution to fitness variation. Using long-term data from sociable weavers (Philetairus socius), a cooperatively breeding bird, we quantified individual sociality as the relative number of strong social bonds within colony-year foraging networks, thereby capturing preferential associations. We estimated the repeatability of individual sociality across years and examined its association with seasonal survival. Survival was estimated using Bayesian multi-state capture-recapture models that accounted for state-dependent detection probabilities. Individual sociality was moderately repeatable across years (R = 0.32, 95% CrI [0.18, 0.47]), indicating consistent differences among individuals despite temporal variation in their social environments. Higher sociality was associated with higher survival in both seasonal periods: high-sociality individuals had higher winter survival than low-sociality individuals, while both medium- and high-sociality individuals had higher summer survival than low-sociality individuals. The overall association was robust to alternative thresholds used to define strong social bonds. Our findings indicate that sociable weavers differ consistently in their relative number of strong social bonds and that these differences are associated with survival. Sociality may therefore contribute to fitness variation and have the potential to be shaped by selection in this system, extending evidence for the adaptive value of strong social relationships across taxa.