Abstract Rapid urban development threatens biodiversity, reducing local livelihoods and well-being when replacing natural habitat by urban structures. Although there is a lot of literature on the effects of urbanization on biodiversity, little has been investigated in South America. This study evaluated, for the first-time, bird community variation in an urban gradient of Nothofagus South-Antarctic forest in Ushuaia, the southernmost city of Argentina. We also studied differences during the breeding season and habitat characteristics. We conducted bird surveys monthly from October 2016 to February 2017 in 12 plots classified as (i) urban, (ii) peri-urban and (iii) non-urban forest. We counted birds for 15 min (three times per month) in each plot to obtain assemblage richness, abundance, density and several indices (Shannon-Weiner diversity, Pielou evenness and abundance-based Chao-Sorensen similarity) for the communities and functional groups. We recorded use of strata, weather conditions and human/domestic animal presence during counting, as well as habitat variables (forest structure, ground cover and understory plants) in each plot. We performed univariate and multivariate analyses, which showed that urbanization positively affects bird community structure (all variables increased in urban forest), with a reduction in the abundance of insectivores cavity-nesters that feed on trees (Campephilus magellanicus, Troglodytes aedon, Aphrastura spinicauda and Pygarrhichas albogularis). Bird assemblages changed similarities over the season; non-urban forests were more dissimilar than urban and peri-urban in October and November, but not in the other months, highlighting different roles of each forest in different periods. We found differences in habitats along the urbanization gradient, and discuss possible influences on bird communities, such as more food supply associated with berry shrubs and low overall richness at high latitudes. According to our results, urban forests with native vegetation are useful structures that help to maintain native bird communities and ecological functions in Ushuaia city.

中文翻译：

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世界最南端城市之一的鸟类群落对原生森林城市化的响应

摘要 当城市结构取代自然栖息地时，快速的城市发展威胁到生物多样性，减少当地生计和福祉。尽管有很多关于城市化对生物多样性影响的文献，但在南美洲却鲜有研究。这项研究首次评估了阿根廷最南端城市乌斯怀亚 Nothofagus South-Antarctic 森林城市梯度中鸟类群落的变化。我们还研究了繁殖季节和栖息地特征的差异。从 2016 年 10 月到 2017 年 2 月，我们每月对 12 个地块进行鸟类调查，这些地块分为 (i) 城市、(ii) 城郊和 (iii) 非城市森林。我们在每个地块中对鸟类进行了 15 分钟（每月 3 次）的计数，以获得组合丰富度、丰度、密度和几个指数（香农 - 韦纳多样性，Pielou 均匀度和基于丰度的 Chao-Sorensen 相似度）为群落和功能群。我们记录了计数过程中地层的使用、天气条件和人类/家畜的存在，以及每个地块中的栖息地变量（森林结构、地被植物和林下植物）。我们进行了单变量和多变量分析，结果表明城市化对鸟类群落结构产生了积极影响（城市森林中的所有变量都增加了），以树木为食的食虫动物窝巢鸟（Campephilus magellanicus、Troglodytes aedon、Aphrastura spinicauda 和Pygarrichicas albogularis)。鸟类组合在整个季节中改变了相似性；非城市森林在 10 月和 11 月与城市和城市周边地区的差异更大，但在其他月份则不然，突出每个森林在不同时期的不同作用。我们发现了沿城市化梯度的栖息地差异，并讨论了对鸟类群落的可能影响，例如与浆果灌木相关的更多食物供应和高纬度地区整体丰富度较低。根据我们的研究结果，具有本地植被的城市森林是有助于维持乌斯怀亚市本地鸟类群落和生态功能的有用结构。