morphology and feather data

Elevational gradients impact organisms in diverse ways due to lower temperatures and oxygen levels at higher elevations. Birds adapt to these constraints through changes in body size, plumage, metabolism, and behaviors such as elevational migration. But whether species show variation across multiple axes of adaptations along a single elevational gradient is not well demonstrated in the literature. The broad elevational distribution of the House Sparrow <i>Passer domesticus</i> in the Himalayas provides a rare insight into whether morphological and plumage modifications can simultaneously arise within a species across its elevational distribution. Drawing insights from eco-physiological patterns, we hypothesized that Sparrows at higher elevations would exhibit larger body sizes (Bergmann’s rule), shorter extremities (Allen’s rule), and a more insulative feather structure. We sampled Sparrows at 13 sites (n = 169) from 300 m to 3500 m along an elevational gradient in the western Himalayas and found that Sparrows at higher elevations were significantly larger following Bergmann’s rule, and had more downy dorsal feathers likely giving higher-elevation Sparrows thermal advantages at low temperatures. We show that House Sparrows may show convergent modifications in response to temperature clines whether they are elevational or latitudinal.

海拔梯度可通过高海拔区域更低的温度与氧气含量，以多样化途径对生物产生影响。鸟类通过体型、羽饰、新陈代谢以及海拔迁徙等行为的改变来适应这些限制条件。但针对单一海拔梯度上，物种是否会在多个适应维度上出现分化这一问题，目前学界尚未有充分的实证研究支持。家麻雀（*Passer domesticus*）在喜马拉雅山脉拥有广泛的海拔分布范围，这为探究同一物种在其整个海拔分布区内是否会同时出现形态学与羽饰特征的适应性改变，提供了难得的研究契机。基于生态生理学的相关研究范式，我们提出如下假说：高海拔区域的家麻雀将表现出更大的体型（伯格曼法则（Bergmann’s rule））、更短的肢体末端（艾伦法则（Allen’s rule）），以及更具隔热性能的羽毛结构。我们沿西喜马拉雅山脉的海拔梯度，在300米至3500米的范围内设置13个采样点，共采集家麻雀样本169份（n=169）。结果发现：高海拔区域的家麻雀体型显著更大，契合伯格曼法则；且其背部绒羽更为发达，这或可帮助高海拔家麻雀在低温环境中获得更好的保温优势。本研究表明，无论温度梯度为海拔梯度还是纬度梯度，家麻雀都可能会产生响应温度梯度的适应性趋同特征。