Step 1 : Introduction to the question "Where on a bird's body is the rachis found?"
...Birds are the only creatures covered with feathers. The various types of feathers each have their own unique function, from insulation and flight to formation of body contours and sensory reception. Feathers are also central to the bird's display behavior used in mating rituals. The typical feather has a central shaft, called the rachis. These are usually pared with branches, or barbs, to form a flattened, curved surface called the vane. Source: Britannica.com