Wild birds respond to flockmate loss by increasing their social network associations to others

Understanding the consequences of losing individuals from wild populations is a current and pressing issue, yet how such loss influences the social behaviour of the remaining animals is largely unexplored. Through combining the automated tracking of winter flocks of over 500 wild great tits (Parus major) with removal experiments, we assessed how individuals' social network positions responded to the loss of their social associates. We found that the extent of flockmate loss that individuals experienced correlated positively with subsequent increases in the number of their social associations, the average strength of their bonds and their overall connectedness within the social network (defined as summed edge weights). Increased social connectivity was not driven by general disturbance or changes in foraging behaviour, but by modifications to fine-scale social network connections in response to losing their associates. Therefore, the reduction in social connectedness expected by individual loss may be mitigated by increases in social associations between remaining individuals. Given that these findings demonstrate rapid adjustment of social network associations in response to the loss of previous social ties, future research should examine the generality of the compensatory adjustment of social relations in ways that maintain the structure of social organization.

探明野生种群个体消失所带来的影响是当前亟待解决的重要议题，但此类个体消失如何影响留存个体的社会行为，目前仍未得到充分探索。本研究结合对500余只野生大山雀（Parus major）冬季种群的自动化追踪技术与移除实验，分析了个体的社会网络地位如何响应其社会伙伴的消失。研究结果显示，个体所经历的同群伙伴消失程度，与其后续社会联结数量、社会纽带平均强度，以及其在社会网络中的整体连通性（定义为边权重总和）呈显著正相关。社会连通性的提升并非由一般性干扰或觅食行为改变所驱动，而是个体为响应伙伴消失而对社会网络的精细联结结构进行调整的结果。因此，个体消失所预期的社会连通性下降，可通过留存个体间社会联结的增加得到缓解。鉴于本研究结果表明，动物会快速调整其社会网络联结以响应原有社会纽带的消失，未来研究应探索维持社会组织结构的社会关系补偿性调整机制的普遍性。