What is the central hollow strut of a feather called?

The central hollow strut of a feather is referred to as the shaft. This structure is crucial because it provides the primary support and structure for the entire feather, allowing it to maintain its shape and function. The shaft runs the length of the feather and is integral in connecting the various parts, such as the vanes, which are the flat part of the feather that actually provides the surface area for insulation and aerodynamics.

The quill is specifically the portion of the shaft that extends from the feather's base and is embedded into the bird's skin at the follicle, acting as an anchor, but it doesn't represent the entirety of the shaft itself. Barbs are the smaller feather components that branch off from the shaft and form the vane, contributing to the feather's functional surface. The vane is created by the barbs on either side of the shaft and plays a role in flight by providing lift and support, but it is not the central strut itself.