Data from: Dominance rank and boldness predict social attraction in great tits

Social relationships can have important fitness consequences and how well an individual is socially connected often correlates with other behavioral traits. Whether such correlations are caused by underlying individual differences in social attraction usually remains unclear, because to identify effects of individual traits on social attraction it is essential to experimentally exclude the influence of the social partner. Using standardized high definition video playback on captive great tits (Parus major), we effectively demonstrate the influence of individual traits on the motivation to be near a conspecific. We show that social attraction varied contrastingly with boldness and stimulus novelty. Shyer birds tended to show stronger social attraction when they were confronted with the stimulus bird for the first time. Lower ranked birds showed the overall strongest social attraction. This rank effect remained after experimentally changing dominance ranks by altering group compositions. Moreover, preference for social association tended to increase with a decrease in dominance rank, suggesting that birds plastically change their social preference in relation to their within-group dominance status. Our results provide insight into how social relations can form and change, processes that are key for understanding the long-term consequences of the social environment on individuals and the consequences certain individuals can have on the social environment.

社会关系对个体适合度具有重要影响，而个体的社会联结程度往往与其他行为特征存在关联。但这类关联是否由个体间社会吸引力（social attraction）的固有差异所导致，通常仍不明确——若要探明个体特征对社会吸引力的调控效应，必须在实验中排除社交伴侣的干扰。本研究通过对圈养大山雀（Parus major）开展标准化高清视频回放实验，有效证明了个体特征对其趋近同种个体（conspecific）的动机具有调控作用。研究发现，社会吸引力与大胆性（boldness）及刺激物新颖性呈反向关联：首次接触刺激鸟时，羞怯程度更高的个体往往表现出更强的社会吸引力；整体而言，等级较低的个体社会吸引力最强。即便通过调整群体组成实验性改变优势等级（dominance rank）后，该等级效应依然存在。此外，社会交往偏好随优势等级降低而增强，表明大山雀可根据其在群体内的优势地位可塑性地调整自身社会偏好。本研究结果揭示了社会关系的形成与变化机制——此类机制是理解社会环境对个体的长期影响，以及特定个体对社会环境所产生影响的核心所在。