Large‐scale spatial gradients of environmental conditions shape organisms, populations and ecosystems. Even though environmental gradients are a key research theme in macro‐ecology and biogeography, the effects of large‐scale, east–west, environmental gradients are largely overlooked compared with north–south gradients. Our study focused on feather moult, an important and energy demanding process in birds. By comparing Western and Eastern Palearctic populations of 21 species, we found that juvenile passerines in the Western and Eastern Palearctic differ in the number of feathers moulted as part of their post‐juvenile moult. This difference is most likely the result of a large‐scale climatic gradient in cold season duration and consequent differences in the time available for moulting. Eastern populations were characterized by a limited extent of feather moult that was additionally affected by migration distance and body mass. The longer migration distance in the Eastern Palearctic caused a generally less extensive moult while high body mass was correlated with a low difference in moult extent between the Western and Eastern Palearctic regions. These results highlight the importance of linking annual cycle processes at the organismal level to the specific environmental conditions within the distribution range of each species.

中文翻译：

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整个古北地区的大规模纵向气候梯度影响着雀形羽毛的蜕皮程度

环境条件的大规模空间梯度影响着生物，种群和生态系统。尽管环境梯度是宏观生态学和生物地理学中的关键研究主题，但与南北梯度相比，大范围的东西向环境梯度的影响还是被忽略了。我们的研究集中在羽毛换羽，这是鸟类中一个重要且耗能的过程。通过比较西部和东部古北洋21种的种群，我们发现西部和东部古北洋中的少年雀形目在其成年后换羽的一部分上换羽的数量不同。这种差异很可能是由于寒冷季节持续时间的大规模气候梯度以及随之而来的换羽时间差异造成的。东部人口的特征是有限的羽毛蜕皮，此外还受到迁徙距离和体重的影响。在东古太平洋，迁徙距离越长，引起的换羽通常就越少，而高体重与西，东古太平洋地区的换毛程度差异较小有关。这些结果凸显了在生物水平上将年度循环过程与每个物种分布范围内的特定环境条件联系起来的重要性。