How feathered are birds? environment predicts both the mass and density of body feathers

1.Studies modelling heat transfer of bird plumage design suggest that insulative properties can be attributed to the density and structure of the downy layer, while waterproofing is the result of the outer layer, comprised of contour feathers. In this study, we test how habitat and thermal condition affect feather mass and density of body feathers (contour, semiplume and downy feathers) measured on the ventral and dorsal sides of the body, using a phylogenetic comparative analysis of 152 bird species. 2.Our results demonstrate that feather mass and the density of downy feathers are higher in species that inhabit colder environments, while total feather density is higher of species breeding under intermediate temperatures compared to the ones breeding under more extreme conditions. The density of contour feathers, depending on the body region, is either quadratically related or negatively correlated to minimum winter temperature. 3.The density of contour and downy feathers, measure...1. 针对鸟类羽衣设计的传热建模研究表明，其隔热性能可归因于绒羽层（downy layer）的密度与结构，而防水性能则由外层的廓羽（contour feathers）所赋予。本研究基于对152种鸟类的系统发育比较分析（phylogenetic comparative analysis），探究了生境与热环境条件如何影响躯体腹侧（ventral）和背侧（dorsal）体表羽毛（包括廓羽、半绒羽（semiplume）及绒羽）的羽毛质量与密度。 2. 研究结果显示，栖息于寒冷环境的鸟类类群，其羽毛质量与绒羽密度更高；而相较于极端温度条件下繁殖的类群，在中等温度环境下繁殖的类群总羽毛密度更高。此外，廓羽密度与身体区域相关，其与冬季最低温要么呈二次相关关系，要么呈负相关关系。 3. 廓羽与绒羽的密度，测量...