Data from: Habitat specialization of birds in the Czech Republic: comparison of objective measures with expert opinion

CAPSULE: Expert-based classification of bird species as habitat specialists and as generalists agrees with objective measures of species’ habitat requirements based on large-scale monitoring data. AIMS: To compare habitat specialization of 137 common bird species breeding in the Czech Republic using three different measures and to test their relationships to species’ abundance and habitat associations. METHODS: Data on bird abundance and surveyed habitats were collected through a standardized monitoring scheme of common breeding species in the Czech Republic. From these data we calculated a quantitative species specialization index (SSI). Canonical correspondence analysis (CCA) was applied to calculate species’ habitat niche breadth and the level of association of each species to the main habitats. A panel of 11 local bird experts classified each species as habitat generalist or habitat
specialist. RESULTS: Species classified as habitat specialists by expert opinion showed higher habitat specialization according to the SSI, as well as according to CCA-based habitat niche breadth. These species were also
more closely associated with one of the main habitat types. These relationships were significant even
after controlling for abundance. CONCLUSIONS: As expert opinion accords with the level of species’ habitat specialization expressed using two quantitative objective measures, we suggest that these characteristics reflect real interspecific variation in the breadth of habitat requirements in birds. Interspecific differences in habitat specialization are not
caused solely by the variability in abundance among species.

核心研究概要（CAPSULE）：专家基于经验将鸟类划分为栖息地专性物种（habitat specialist）与栖息地广适性物种（habitat generalist）的分类结果，与基于大规模监测数据得到的物种栖息地需求客观量化指标具有一致性。

研究目的（AIMS）：采用三种不同量化方法，比较在捷克共和国繁殖的137种常见鸟类的栖息地特化程度，并检验其与物种多度及栖息地关联的相关性。

研究方法（METHODS）：通过针对捷克共和国常见繁殖鸟类的标准化监测方案，收集鸟类多度与调查栖息地的相关数据。基于上述数据，我们计算得到量化的物种特化指数（Species Specialization Index, SSI）。采用典范对应分析（Canonical Correspondence Analysis, CCA）计算物种的栖息地生态位宽度，以及各物种与主要栖息地的关联程度。由11位本地鸟类专家组成的专家组，将每个物种划分为栖息地广适性物种或栖息地专性物种。

研究结果（RESULTS）：经专家分类的栖息地专性物种，其物种特化指数（SSI）以及基于典范对应分析（CCA）得到的栖息地生态位宽度均体现出更高的栖息地特化程度。此类物种同时与某一类主要栖息地类型具有更强的关联性。即便在控制物种多度的影响后，上述关联仍具有统计学显著性。

研究结论（CONCLUSIONS）：由于专家分类结果与两种基于客观量化方法得到的物种栖息地特化程度具有一致性，本研究认为上述特征可反映鸟类物种间栖息地需求宽度的真实种间差异。鸟类栖息地特化程度的种间差异并非仅由物种间的多度差异所导致。