Gelatin to make preservatives. Eggs and meat for food protein. Birds are nice company as pets. Ideas for aerodynamic designs. Some birds do not have feathers.
Feathers are flexible but very weak.
Feathers can move fast but they are not very strong. Feathers are light but very strong. In between the flight feather tracks is fluffy down. The wing is shaped by the wind. The wing is shaped by the bird's beak.