The Presence and Microstructure of Down Components of Feathers in Nineteen Orders of Birds (Aves)

We used light and raster electron microscopy to study for the first time in research the microstructure of the down parts of feather vanes consisting of combined barbules (“barbule I”) provided with both typical plumulaceous barbules (“barbicel,” “barbule II”) and modified plumulaceous barbules (MBs). Their presence and distribution over different pterylae were studied on 3330 feathers from 441 birds of 129 species belonging to 45 families of 19 orders. Information about the presence of afterfeathers and of umbilical barbs on feathers was clarified. Modified plumulaceous barbules were found on feathers of all species studied, more often on coverts, less often on wing and tail feathers. Down components were studied in most detail in the orders Charadriiformes and Passeriformes; in the former, the presence or absence of MB was specific at the level of family or genus, while in the latter, afterfeathers or umbilical barbs were never found together on the same feather. The possibility is discussed of using various combinations of down components and features of their microstructure as an important addition to the integrated system of ptilological taxa identification by feathers (including single feathers) and in some cases even by the pteryla to which the tested feather belongs.