Feathers have been used to steer arrows for many centuries. The shooting characteristics of feathers are the reason they are still excellent for arrows.
Feathers are able to fold flat as the arrow passes the bow. This makes them forgiving of any error in the execution of the shot. Feathers also provide good drag and by this steer the arrow very positively. They can be set at an angle to the shaft or straight and use their natural curl to provide stabilising spin in flight. In wet conditions the flight characteristic of the arrow can change and it is worth keeping them relatively dry so as to have your arrows shoot as they would in a dry day. The weight of any moisture absorbed by the feathers can change the balance of the arrow and change the sight marks achieved as compared with a dry day.
Still a favourite with many and a must for Longbow and Traditional Archery, plus excellent at short distance and indoors. Pretty looking too.