Data for: Neotropical mixed-species bird flocks in a community context

<b>Abstract</b><br/><p>Mixed-species flocks are an important component of bird communities, particularly in the Neotropics, where flocks reach their highest diversity. The extent to which mixed-species flocks represent unique functional or ecological roles within communities, and how these attributes change over environmental gradients, however, is not well understood. We use a trait-based approach to examine functional aspects of flocking assemblages as they relate to those observed in the larger avian community across a 3000 m elevational gradient. Our results reveal similar ecological strategies among flocking species and the communities in which they occur, at the scale of the regional pool and across elevations. Trait variation in flocking and non-flocking assemblages is structured along two major axes defined by size- and resource-related traits. The trait space occupied by flocking species, however, represents only half (51%) that of the larger community. Similarly, the trait space of flocks across elevations is restricted compared to non-flocking species. The shared trait space across flock types represents small-bodied invertivores foraging in lower forest strata, traits associated with increased vulnerability to predation. The concentration of flocking species in functional trait space suggests high niche packing and either more overlap in ecological strategies or more finely divided niches relative to non-flocking species.</p>

<b>摘要</b><br/><p>混合物种种群鸟群（mixed-species flocks）是鸟类群落的重要组成部分，在新热带区（Neotropics）尤为突出，该区域的混群鸟类多样性达到最高水平。然而，学界对混合物种种群鸟群在群落中所承载的独特功能或生态角色的覆盖范围，以及这些属性如何随环境梯度发生演变，仍缺乏深入认知。本研究采用性状导向的研究范式，在跨度达3000米的海拔梯度（elevational gradient）上，剖析混群鸟类集合群的功能特征，并将其与更大尺度的鸟类群落特征进行关联分析。研究结果表明，无论是在区域物种库尺度还是不同海拔区域，混群鸟类与其所在群落均展现出趋同的生态策略。混群与非混群鸟类集合群的性状变异，主要沿体型与资源相关性状所定义的两大主轴进行分布。但混群物种所占据的功能性状空间仅为整个鸟类群落的一半（51%）。与之类似，相较于非混群物种，不同海拔的混群鸟类的性状空间也更为受限。各类混群鸟类共有的性状空间指向一类在较低森林层位觅食的小型食虫动物（invertivores），这类性状特征与更高的被捕食脆弱性密切相关。混群物种在功能性状空间中的集中分布，提示其生态位填充程度更高，且相较于非混群物种，它们要么具备更高的生态策略重叠度，要么拥有更为精细的生态位划分。</p>