Liao Chun-Chieh, Ding Tzung-Su, Chen Chao-Chieh
School of Forestry and Resource Conservation National Taiwan University Taipei Taiwan.
Division of Ecology and Evolution Research School of Biology Australian National University Canberra Australian Capital Territory Australia.
Ecol Evol. 2022 Feb 18;12(2):e8608. doi: 10.1002/ece3.8608. eCollection 2022 Feb.
A mixed-species bird flock is a social assemblage where two or more bird species are moving together while foraging and might benefit from increased foraging efficiency and antipredator vigilance. A "mega-flock," which includes flocking species from different vegetation strata, often exhibits high species diversity. Mechanisms for the formation of mega-flocks have not yet been explored. In this study, we evaluated the influence of vegetation structure and bird species diversity in driving the occurrence of mega-flocks. We investigated the composition of mixed-species flocks, local bird communities, and vegetation structure in five vegetation types of two high-elevation sites in central Taiwan. Mega-flocks occurred more frequently in pine woodland than later successional stages of coniferous forests. However, species richness/diversity of local bird communities increased along successional stages. Therefore, vegetation variables exhibit more influence on the occurrence of mega-flocks than local bird communities. Besides foliage height diversity, understory coverage also showed positive effects on flock size of mixed-species flocks. Our results indicated that pine woodlands with more evenly distributed vegetation layers could facilitate the interactions of canopy and understory flocks and increase the formation of mega-flocks and thus the complexity of mixed-species flocks.
混合物种鸟群是一种社会群体，其中两种或更多种鸟类在觅食时一起活动，可能会从提高觅食效率和反捕食警惕性中受益。“超级鸟群”包括来自不同植被层的群居物种，通常表现出高物种多样性。超级鸟群形成的机制尚未得到探索。在本研究中，我们评估了植被结构和鸟类物种多样性对超级鸟群出现的影响。我们调查了台湾中部两个高海拔地点五种植被类型中混合物种鸟群的组成、当地鸟类群落和植被结构。超级鸟群在松树林中出现的频率高于针叶林的后期演替阶段。然而，当地鸟类群落的物种丰富度/多样性随着演替阶段而增加。因此，植被变量对超级鸟群出现的影响比当地鸟类群落更大。除了叶高多样性外，林下覆盖率对混合物种鸟群的群体大小也有积极影响。我们的结果表明，植被层分布更均匀的松树林可以促进冠层和林下鸟群的相互作用，增加超级鸟群的形成，从而增加混合物种鸟群的复杂性。
