Kaepora Gaebora

Kaepora Gaebora (ケポラ・ゲボラ, Kepora Gebora) is an owl introduced in Ocarina of Time. He is both very large and very knowledged, traits he uses to carry the Hero places and to advice him on the next course of his quest.

In Ocarina of Time, Kaepora Gaebora is said by a Gossip Stone to be the reincarnation of an ancient sage. It is therefore not unlikely his Ocarina of Time and Four Swords Adventures incarnations are the same character. It also helps explain why he knows so much about Hyrule and why he keeps track of Link's proceedings.

Ocarina of Time
He is strong enough to carry young Link through the air, and can do so repeatedly in certain locations, such as the top of Death Mountain down to Kakariko Village, and also from Lake Hylia to the drawbridge just outside Hyrule Market. He is not seen after Link draws the Master Sword from its pedestal save for when Link learns the Requiem of Spirit, and after he obtains the Silver Gauntlets.

Majora's Mask
In the alternate dimension of Termina, the wise owl too has a counterpart. He taught Link the Song of Soaring, which allowed Link to warp to different activated owl statues. He is seen again at Snowhead, where he tells Link where the Lens of Truth is and helps him get to the cave where it is placed by using his feathers to show you a group of invisible platforms that Link can use to reach the cave.

Four Swords Adventures
Kaepora Gaebora himself makes a reappearance in Four Swords Adventures, serving much the same role he did in Ocarina of Time.

Theories
Sage identity - Being said to be the reincarnation of an ancient Sage, Kaepora Gaebora is subject to much speculation on his original identity. It is often argued that Kaepora Gaebora is Rauru's form outside of the Sacred Realm. This assumption is based on one of the Gossip Stones' message that "its character is rather lighthearted", which is thought to be a reference to Rauru's status as the Sage of Light. However, Kaepora Gaebora states that he did not believe in "the tales of a boy who could travel back and forth through time, whereas Rauru was the very person who caused that time travel. And this is merely the most prominent example of several quotes of the two characters that just don't add up if they were to be the same person. Another popular suggestion is that Kaepora Gaebora is the reincarnation of Kasuto - a theoretical Sage assumed to exist due to Ocarina of Time ' s system of naming its Sages after towns from The Adventure of Link.

Trivia
Owls are a common theme throughout the The Legend of Zelda, usually, indeed, in relation to the gaining of knowledge. If and how there is a connection with Kaepora Gaebora is largely unknown.
 * In Link's Awakening, there is an owl character who guides Link with words of wisdom. Since both Kaepora Gaebora and this owl are owls who give Link directions, it is possible that the owl from Link's Awakening may have inspired the later Kaepora Gaebora. From an in-universe perspective, it is possible that the two's likeness is to be explained the other way around. Since all characters from Koholint are a product of either Link's or the Wind Fish's minds, in some cases obviously inspired by someone they know, possibly the memory of Kaepora Gaebora created the owl.
 * Eldin, the Light Spirit of the Eldin Province in Twilight Princess, is also an owl or perhaps another kind of a large bird.
 * Owl Statues appear in Link's Awakening, even moreso in its DX version Oracle of Ages, Oracle of Seasons and Twilight Princess. They either serve to hand out information and hints on nearby challenges or to warp Link to another location.