Abstract

Increasing human activity is altering the structure of forests, which affects the composition of communities, including birds. However, little is known about the key forest structure variables that determine the richness of bird communities in European temperate oak forests. We, therefore, aimed to identify key variables in these habitats that could contribute to the design of management strategies for forest conservation by surveying 11 oak-dominated forest sites throughout the mid-mountain range of Hungary at 86 survey points to reveal the role of different compositional and structural variables for forest stands that influence the breeding bird assemblages in the forests at the functional group and individual species levels. Based on decision tree modelling, our results showed that the density of trees larger than 30 cm DBH was an overall important variable, indicating that large-diameter trees were essential to provide diverse bird communities. The total abundance of birds, the foliage-gleaners, primary and secondary cavity nesters, residents, and five specific bird species were related to the density of high trunk diameter trees. The abundance of shrub nesters was negatively influenced by a high density of trees over 10 cm DBH. The density of the shrub layer positively affected total bird abundance and the abundance of foliage gleaners, secondary cavity nesters and residents. Analysis of the co-dominant tree species showed that the presence of linden, beech, and hornbeam was important in influencing the abundance of various bird species, e.g., Eurasian Treecreeper (Certhia familiaris), Marsh Tit (Poecile palustris) and Wood Warbler (Phylloscopus sibilatrix). Our results indicated that large trees, high tree diversity, and dense shrub layer were essential for forest bird communities and are critical targets for protection to maintain diverse and abundant bird communities in oak-dominated forest habitats.

中文翻译：

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高大直径的树木和茂密的灌木层是橡树为主的森林中鸟类群落丰度和组成的关键决定因素

摘要

人类活动的增加正在改变森林的结构，从而影响包括鸟类在内的群落的组成。然而，人们对决定欧洲温带橡树林鸟类群落丰富度的关键森林结构变量知之甚少。因此，我们的目标是确定这些栖息地中的关键变量，这些变量有助于设计森林保护管理策略，方法是对匈牙利中山区 11 个以橡树为主的森林点进行 86 个调查点的调查，以揭示不同物种在森林保护中的作用。林分的组成和结构变量在功能类群和个体物种层面上影响森林中的繁殖鸟类组合。基于决策树模型，我们的结果表明，直径大于 30 厘米的树木的密度是一个重要的变量，这表明大直径的树木对于提供多样化的鸟类群落至关重要。鸟类、树叶拾遗者、初级和次级洞穴筑巢者、留鸟和五种特定鸟类的总丰度与高树干直径树木的密度有关。灌木巢鸟的丰度受到胸径超过 10 厘米的高密度树木的负面影响。灌木层的密度对鸟类的总丰度以及树叶拾穗鸟、次生空巢鸟和居民的丰度产生积极影响。对共同优势树种的分析表明，椴树、山毛榉和角树的存在对于影响各种鸟类的丰度具有重要意义，例如欧亚树爬山雀（Certhiaamilis）、沼泽山雀（Poecilepalustris）和林莺（Phylloscopus）西比拉克斯）。我们的研究结果表明，高大的树木、高的树木多样性和茂密的灌木层对于森林鸟类群落至关重要，也是保护以橡树为主的森林栖息地保持多样化和丰富的鸟类群落的关键目标。