The microstructure of white feathers predicts their visible and near-infrared reflectance properties

Research on the optical properties of animal integuments, including fur, feather, skin and cuticle, has focussed almost exclusively on animal-visible wavelengths within the narrow range of 300 - 700 nm. By contrast, the near-infrared (NIR) portion of direct sunlight, spanning 700 - 2600 nm, has been largely ignored despite its potentially important thermal consequences. We quantified variation in visible and NIR reflectance and transmission for white body contour feathers of 50 bird species, and examined how well they are predicted by feather macro- and micro-structural morphology. Both visible and NIR reflectance of the feathers varied substantially across species. Larger, thicker, and sparser feathers that are characteristic of larger species, and feathers with rounder barbs and more closely spaced barbules, had high average reflectance, particularly within avian-visible wavelengths (300 - 700 nm). Feathers with rounder barbs and more closely situated barbules also had high average re...针对动物体表覆盖物（animal integuments）——包括毛发、羽毛、皮肤与角质层——的光学特性研究，几乎仅聚焦于300~700 nm这一窄波段内的动物可见波长范围。与之形成鲜明对比的是，占直射太阳光700~2600 nm波段的近红外（near-infrared, NIR）部分，尽管其可能带来重要的热效应，却长期被学界忽略。我们量化了50个鸟类物种的白色体廓羽在可见光与近红外波段的反射率与透射率变化，并探究了羽毛宏观与微观结构形态对其光学特性的预测能力。不同鸟类的羽毛在可见光与近红外波段的反射率均存在显著差异。体型更大的物种所特有的更大、更厚且更稀疏的羽毛，以及具有更圆羽枝（barbs）和间距更紧密羽小枝（barbules）的羽毛，其平均反射率更高，尤其是在鸟类可见波段（300~700 nm）范围内。而具有更圆羽枝与更紧密排列羽小枝的羽毛，其平均反...