ABSTRACT Mixed-species flocks are ubiquitous in forest bird communities, yet the extent to which positive (facilitative) or negative (competitive) interactions structure these assemblages has been a subject of debate. Here, we describe the fine-scale foraging ecology and use network analysis to quantify mixed-species flocking interactions of an insectivorous bird community in hardwood forests of north-central Florida. Our goal was to determine if similarly foraging species are more (facilitation hypothesis) or less (competition hypothesis) likely to associate in flocks, and if foraging ecology can explain intraspecific abundance patterns within flocks. We quantified attack maneuvers, foraging substrate, and foraging microhabitat of all 17 common insectivorous species in these forests and characterized the composition of 92 flocks encountered. Flocking was important in our community; 14 of 17 species joined more than 5% of flocks, and 10 species had flocking propensities of over 0.80. Our results supported both hypothesized mechanisms structuring flock composition. Species had distinct, well-defined foraging niches during the nonbreeding season, but foraging niche overlap among flocking species was greater than expected by chance. Consistent with the facilitation hypothesis, we found that similarly foraging species were significantly more likely to associate in flocks, a result driven by lower association strengths in large-bodied woodpeckers. We found no evidence of assortment by foraging behavior, however, likely because foraging behavior and substrate use showed strong niche partitioning at the fine scale within our community. Intraspecific abundance patterns were significantly linked to foraging substrate use, with live leaf use correlated with high within-flock abundance and relative abundance at study sites. Species that specialized on comparatively less abundant substrates (tree trunks, epiphytes, dead leaves) joined flocks as singletons, showed lower relative abundance, and may exhibit nonbreeding territoriality. Our results highlight the importance of foraging substrate use and mixed-species flocks in structuring the nonbreeding ecology of migratory birds.

中文翻译：

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相似的觅食者会聚集在一起吗？亚热带地区非繁殖觅食行为及其对混种群聚的影响

摘要 混合物种群在森林鸟类群落中无处不在，但这些组合的积极（促进）或消极（竞争）相互作用在多大程度上构成了争论的主题。在这里，我们描述了细尺度觅食生态学，并使用网络分析来量化佛罗里达州中北部硬木森林中食虫鸟类群落的混合物种集群相互作用。我们的目标是确定类似的觅食物种是否更多（促进假设）或更少（竞争假设）可能在鸡群中关联，以及觅食生态学是否可以解释鸡群内的种内丰度模式。我们量化了这些森林中所有 17 种常见食虫物种的攻击机动、觅食基质和觅食微栖息地，并表征了遇到的 92 个鸡群的组成。植绒在我们的社区中很重要；17 个物种中有 14 个加入了超过 5% 的群体，10 个物种的植绒倾向超过 0.80。我们的结果支持了构建鸡群组成的两种假设机制。在非繁殖季节，物种具有明显的、明确的觅食生态位，但植绒物种之间的觅食生态位重叠偶然大于预期。与促进假说一致，我们发现类似觅食的物种更有可能在群体中联合，这是由于大型啄木鸟的联合强度较低所致。然而，我们没有发现觅食行为分类的证据，这可能是因为觅食行为和基质使用在我们社区内的精细尺度上显示出强大的生态位划分。种内丰度模式与觅食基质的使用显着相关，活叶的使用与研究地点的高群内丰度和相对丰度相关。专门在相对较少的基质（树干、附生植物、枯叶）上繁殖的物种以单身形式加入羊群，表现出较低的相对丰度，并且可能表现出非繁殖领土。我们的结果强调了觅食基质使用和混合物种群在构建候鸟非繁殖生态方面的重要性。并且可能表现出非繁殖领土。我们的结果强调了觅食基质使用和混合物种群在构建候鸟非繁殖生态方面的重要性。并且可能表现出非繁殖领土。我们的结果强调了觅食基质使用和混合物种群在构建候鸟非繁殖生态方面的重要性。