Increasing temperatures associated with climate change are predicted to cause reductions in body size, a key determinant of animal physiology and ecology. Using a four-decade specimen series of 70 716 individuals of 52 North American migratory bird species, we demonstrate that increasing annual summer temperature over the 40-year period predicts consistent reductions in body size across these diverse taxa. Concurrently, wing length - an index of body shape that impacts numerous aspects of avian ecology and behaviour - has consistently increased across species. Our findings suggest that warming-induced body size reduction is a general response to climate change, and reveal a similarly consistent and unexpected shift in body shape. We hypothesise that increasing wing length represents a compensatory adaptation to maintain migration as reductions in body size have increased the metabolic cost of flight. An improved understanding of warming-induced morphological changes is important for predicting biotic responses to global change.

中文翻译：

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北美候鸟全球变暖的共同形态后果。

预计与气候变化相关的温度升高会导致体型减小，这是动物生理学和生态学的关键决定因素。我们使用了四个十年的标本系列，对北美52种候鸟物种的70,716个个体进行了研究，结果表明，在40年的时间内，每年夏季气温的升高预示着这些不同类群的体型会持续减小。同时，机翼长度（影响鸟类生态和行为各个方面的体形指标）在各个物种中一直在增加。我们的研究结果表明，变暖导致的体型缩小是对气候变化的普遍反应，并揭示了类似一致且出乎意料的体型变化。我们假设随着机翼尺寸的减小增加了飞行的代谢成本，增加机翼长度代表了补偿性适应，以维持迁徙。更好地了解气候变暖引起的形态变化对于预测生物对全球变化的反应非常重要。