SummaryMediterranean mountains are biodiversity hotspots where northern species occur surrounded by drier and warmer lowlands. In this context, global warming is pushing these species to higher elevations. This paper assesses whether forest birds have experienced a shift upwards over the elevation gradient in the last 35 years in the Guadarrama Mountains (600–2,400 m asl; central Spain). Alternatively, the paper tests whether the reported shifts are related to changes in forest structure resulting from rural abandonment and/or forest management. To do this, sampling carried out from 1976 to 1980 along the elevation gradient was repeated in 2014–2015. In addition, the habitat preferences of birds were used to test if the elevation shifts were related to changes in forest structure. Results show that the mean range position of birds associated with tree cover shifted downwards, a trend supported by an increase in tree-dependent birds at mid-elevations. These trends suggest that an increase in tree cover has buffered the altitudinal shifts of forest birds predicted by climate warming. Results also suggest that proper forest management may improve the resilience of forest bird communities to the pervasive effects of climate warming.

中文翻译：

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地中海山脉森林鸟类的海拔变化：原因和保护前景

摘要地中海山区是生物多样性热点地区，北部物种分布在更干燥、更温暖的低地周围。在这种情况下，全球变暖正在将这些物种推向更高的海拔。本文评估了在过去 35 年中，瓜达拉马山脉（600-2,400 m asl；西班牙中部）的森林鸟类是否经历了海拔梯度的上升。或者，本文测试了报告的变化是否与农村放弃和/或森林管理导致的森林结构变化有关。为此，从 1976 年到 1980 年沿海拔梯度进行的采样在 2014-2015 年重复进行。此外，鸟类的栖息地偏好被用来测试海拔变化是否与森林结构的变化有关。结果表明，与树木覆盖相关的鸟类的平均范围位置向下移动，这一趋势得到了中海拔地区依赖树木的鸟类增加的支持。这些趋势表明，树木覆盖率的增加缓冲了气候变暖所预测的森林鸟类的高度变化。结果还表明，适当的森林管理可以提高森林鸟类群落对气候变暖普遍影响的抵御能力。