Different types of social links contrastingly shape reproductive traits in a multi-level society of wild songbirds

Social environments can influence individuals’ health, reproductive success, welfare, and survival. These environments consist of diverse social connection types at multiple levels, which could influence different components of fitness in contrasting ways. Great tits (Parus major) exhibit a multilevel society with four major types of dyadic bonds: pair mates, breeding neighbours, flockmates, and spatial associates, all of which can influence fitness. Here, we show that these different types of dyadic bonds are differentially linked with reproductive success metrics in a wild great tit population, and that the consideration of spatial effects could provide further insights into these interrelationships. Specifically, more-social individuals had more fledglings, those that bonded more strongly with their pairmate laid earlier, and those with more spatial associates laid smaller clutches. These findings highlight the importance of considering multiple types of dyadic relationships when identifying the fitness consequences of sociality, and the need for work to experimentally test these relationships, particularly in spatially structured populations.