Abstract

The adaptive significance of flocking in birds has been long debated. In particular, the formation of flocks is thought to increase foraging efficiency and reduce predation pressure. Such benefits can compensate for the costs of flocking including increased competition for resources. The evolution of flocking among species is thus likely shaped by ecological factors related to food abundance and distribution and the level of predation risk experienced during foraging. Comparative analyses have been particularly helpful to identify ecological correlates of group living in many taxa. Yet, no comprehensive comparative analysis of flocking at the species level has been performed in birds using a phylogenetic framework. I conducted a phylogenetically-based comparative analysis of flocking using a large number of species (> 1000) from different families found across the world and examined the effect of many ecological and life history variables related to food distribution and abundance and predation risk. The analysis revealed that flocking at the species level can be predicted reasonably well (R² = 28%) from a set of ecological and life history variables including diet, timing of activity, foraging substrate, clutch size, and annual adult survival. In particular, flocking was more prevalent in species with a plant diet, in aquatic species, and in species with fast life histories. The results generally support the idea that resource abundance and distribution and perceived predation risk during foraging have shaped the evolution of flocking in birds.

Significance statement

Why birds form flocks during foraging has been long debated. Flocking like other types of group living has probably been shaped over evolutionary times by ecological factors related to food abundance and distribution and predation risk while foraging. Comparative analyses have identified several ecological correlates of group living in many taxa but have yet to be performed comprehensively in birds. Here, I conducted a phylogenetically-based comparative analysis of flocking using a large number of species (> 1000) found across the world to examine the effect of many ecological and life history variables related to food distribution and abundance and predation risk. The analysis revealed that flocking was more prevalent in species with a plant diet, in aquatic species, and in species with slow life histories. The results generally support the idea that resource abundance and distribution and perceived predation risk during foraging have shaped the evolution of flocking in birds.

中文翻译：

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鸟类的植绒与饮食、觅食基质、活动时间和生活史有关

摘要

长期以来，人们一直在争论成群结队对鸟类的适应性意义。特别是，羊群的形成被认为可以提高觅食效率并降低捕食压力。这些好处可以补偿植绒的成本，包括增加对资源的竞争。因此，与食物丰度和分布相关的生态因素以及觅食过程中经历的捕食风险水平可能会影响物种间群聚的演变。比较分析特别有助于确定生活在许多分类群中的群体的生态相关性。然而，尚未使用系统发育框架对鸟类进行物种水平的综合比较分析。我使用大量物种进行了基于系统发育的比较分析（> 1000) 来自世界各地的不同家庭，并检查了许多与食物分布、丰度和捕食风险相关的生态和生活史变量的影响。分析表明，可以很好地预测物种水平的植绒（R ²  = 28%) 来自一组生态和生活史变量，包括饮食、活动时间、觅食基质、离合器大小和成年成年存活率。特别是，植绒在以植物为食的物种、水生物种和具有快速生活史的物种中更为普遍。结果普遍支持这样一种观点，即资源丰富和分布以及觅食过程中感知到的捕食风险影响了鸟类群聚的演变。

意义陈述

Why birds form flocks during foraging has been long debated. Flocking like other types of group living has probably been shaped over evolutionary times by ecological factors related to food abundance and distribution and predation risk while foraging. Comparative analyses have identified several ecological correlates of group living in many taxa but have yet to be performed comprehensively in birds. Here, I conducted a phylogenetically-based comparative analysis of flocking using a large number of species (> 1000) found across the world to examine the effect of many ecological and life history variables related to food distribution and abundance and predation risk. The analysis revealed that flocking was more prevalent in species with a plant diet, in aquatic species, and in species with slow life histories. The results generally support the idea that resource abundance and distribution and perceived predation risk during foraging have shaped the evolution of flocking in birds.