Unfavourable environment limits social conflict in Yuhina brunneiceps.

Identifying the factors that modulate cooperative and competitive behaviours is the key to understanding social evolution. However, how ecological factors affect social conflict and their fitness consequences remain relatively unexplored. Here, using both a game-theoretical model and empirical data, we show that Taiwan yuhinas (Yuhina brunneiceps)--a joint-nesting species in which group members are unrelated--employ more cooperative strategies in unfavourable environmental conditions.