Multiple effects of weather on common waxbill group foraging and social behavior

The weather poses challenges for wildlife. Environmental challenges can be responded to at the group level by social animals, but the influence of weather on group behavior is poorly understood. We investigated how the weather affects behavior in a gregarious species by monitoring common waxbills (Estrilda astrild) in a large mesocosm during five years. We found seasonal patterns on collective foraging, aggressiveness, and the structure of the social network, usually showing two cycles per year: one peaking in Spring and a smaller one in late Summer. Controlling for seasonality, we found behavioral changes related to increased energy demands on colder and/or cloudier days, such as more frequent and larger foraging groups that resulted in less structured social networks. Rain and wind disturb movement, and we found that on rainy days foraging group journeys became briefer and more synchronous, resulting in stronger associations between individuals and less structured networks, and that on windy days foraging groups were less frequent, larger, and with more within-group aggression. The results show that the weather has more varied effects than anticipated on ecologically-relevant group behavior. We discuss how such weather-related effects can improve predictions of how social animals will react to environmental changes.