Defense, vigilance, and optimal foraging are frequently related to the formation of flocks in birds. Few studies concerning long-distance migrant shorebirds analyzed whether phylogeny and ecological similarities of species are associated with the formation of heterospecific flocks. Here, we explore (1) the niche conservatism theory, (2) the competition-relatedness hypothesis, and (3) the niche construction hypothesis to explain the formation of wintering Nearctic-Neotropical heterospecific shorebird flocks in the southeastern coast of Brazil. In the first, closely-related species keep their ecological traits over time. In the last two hypotheses, ecological dissimilar and distant-related species may coexist due to strong biotic interactions. Our results discard the influence of relatedness between species and/or phylogenetic filtering signals that could act in the formation of heterospecific flocks. Co-participation of species in flocks is explained by similarities in body weight and tarsus length, which invokes the niche construction hypothesis. Probably, some similar-sized and niche-constructing species are relocating in space and changing the environment that they experience to optimize individual capacity to flee from predators. From an ecological perspective, numerous phenotypically similar species with redundant roles could lead to greater resilience of the community under anthropogenic disturbances. From an evolutionary perspective, different species with similar phenotypes may diminish costs of activity matching and augment individual fitness.

中文翻译：

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解开异种近北-新热带滨鸟群形成背后的非生物和生物机制

防御、警惕和最佳觅食通常与鸟类群的形成有关。很少有关于远距离迁徙滨鸟的研究分析物种的系统发育和生态相似性是否与异种群的形成有关。在这里，我们探讨了 (1) 生态位保守主义理论、(2) 竞争相关性假设和 (3) 生态位构建假设，以解释巴西东南沿海越冬的近北-新热带异种滨鸟群的形成。首先，密切相关的物种会随着时间的推移保持其生态特征。在后两个假设中，由于强烈的生物相互作用，生态异种和远缘物种可能共存。我们的结果忽略了物种和/或系统发育过滤信号之间的相关性的影响，这些信号可能会影响异种特定群体的形成。群体中物种的共同参与可以通过体重和跗骨长度的相似性来解释，这引发了生态位构建假设。或许，一些体型相似和生态位构建的物种正在太空中重新定位并改变它们所经历的环境，以优化个体逃离捕食者的能力。从生态学的角度来看，许多表型相似且具有冗余作用的物种可能会导致社区在人为干扰下具有更大的恢复能力。从进化的角度来看，具有相似表型的不同物种可能会降低活动匹配的成本并增强个体适应性。