Positive relationships between association strength and phenotypic similarity characterize the assembly of mixed-species bird flocks worldwide

Competition theory predicts that communities at small spatial scales should consist of species more dissimilar than expected by chance. We find a strikingly different pattern in a multi-continent dataset (55 presence-absence matrices from 24 locations) on the composition of mixed-species bird flocks, important subunits of local bird communities the world over. Using null models and randomization tests followed by meta-analysis, we find the association strength of species in flocks to be strongly related to similarity in body size and foraging behavior, and higher for congeneric compared with non-congeneric species pairs. Given the small spatial scale of our individual analyses, differences in habitat preferences of species are unlikely to have caused these association patterns; therefore, the patterns are most likely the outcome of species interactions. Extending group-living and social information use theory to a heterospecific context, we discuss potential behavioral mechanisms leadin...竞争理论预测，小空间尺度下的群落其组成物种间的相似程度应低于随机预期水平。我们在一项跨大洲数据集（涵盖24个采样点的55张物种出现-缺失矩阵（presence-absence matrix））中，针对全球各地本地鸟类群落的重要组成亚单元——混合物种种鸟群（mixed-species bird flocks）的组成格局展开分析，却发现了截然不同的格局。我们通过零模型（null models）、随机化检验并结合元分析（meta-analysis）方法开展研究，发现鸟群内物种间的关联强度与体型大小、觅食行为的相似性显著相关，且同属物种种对的关联强度高于非同属物种种对。鉴于各单次分析均基于小空间尺度，物种的栖息地偏好差异不太可能解释此类关联格局，因此该格局极大概率源自物种间的相互作用。我们将群居生活与社会信息利用理论拓展至异种（heterospecific）互动情境，探讨了潜在的行为机制——（原文至此截断）