Windy weather drives social structure in wild zebra finches

Social connections provide individuals with multiple benefits. Individuals, however, are often constrained in how they socially organize due to ecological and environmental factors that affect individual space-use and movement patterns. Weather is one such factor that influences individual movements, and thus social structure. While on longer time scales (i.e., seasonally) the impacts of weather are relatively predictable, on shorter time scales (i.e., sub-daily), the impacts of weather on social organization are less predictable yet are largely overlooked. In this study, we examined the influence of short-term weather components, specifically wind and temperature, on the social structure of free-living zebra finches (Taeniopygia castanotis) in the Australian arid zone. Our goal was to characterize if social network structure was impacted by hourly changes in these important weather components. To do so, we used an automated radio telemetry system to concurrently track 128 wild zebra finches for 12 consecutive days in the Australian spring in order to examine the relationships between weather components and social structure. Using Bayesian network analyses to account for the uncertainty in association strengths among individuals, we examined network structure, as measured by density and modularity, in relation to hourly wind speed, temperature, and time of day. Additionally, to assess if weather impacted the synchronization of group-level movements, we calculated proximity ratios between neighbouring individuals, which we related to wind and temperature. We observed that network modularity increased during hours with higher mean wind speed and was highest in the morning and evening hours. In contrast, network density was not related to wind speed. Additionally, neither modularity nor density showed a significant relationship with temperature during the tracking period, however, this period did not cover a large temperature gradient. Group-level movement patterns as measured by proximity ratios between neighbouring individuals showed no relationship with either wind or temperature. Our results suggest that changes in wind impact social structure in zebra finches. Given the critical role that network modularity plays in social information transfer, increased wind could have important downstream consequences. Stochastic and more frequent changes in weather due to climate change could thus potentially disproportionately impact species, such as the nomadic zebra finch, that rely on locating ephemeral resources.