what is the tegmen around the rachis of a waterfowl
If you look on the underside of most waterfowl primary feathers, you will notice a shiny, waxy-looking area on the barbs along the edge of the rachis. This is called tegmen but is often referred to as the 'Blood Line', although there is no blood within the fibres. The tegmen area of the barbs are thick, triangular in shape and have no barbules which means that they do not marry well together.