See how often they participate in the script: HERE.
Character Story: Cuccos are the chickens found throughout the game. They will eventually retaliate if Link attacks them for a long enough period of time. Link can also lift them above his head and use them to fly for short distances.
Race Story: Animals appear all throughout Hyrule and are often often helpful in their own ways, either directly or through subtle advice. Link can talk to them when he is in his wolf form.