Seagull

Link can control them in TWW using a Hyoi Pear. At the Forsaken Fortress, several of them circle around the window of the room in which Aryll is being held captive. They sometimes fly alongside The King of Red Lions, Link's boat.

Link's telescope from Aryll is decorated with seagulls on one side.

If you get through Link's Awakening without dying once, Marin will be transformed into a seagull.

Seagulls are known to flock near Big Octos in a circle, it is unknown whether or not the number of seagulls signifies the Octo's eyes or not.

Trivia
In Phantom Hourglass, you can shoot the seagulls with the cannon on your ship.