Kaepora Gaebora
A wise sage that roams the skies of Hyrule. Although his appearance renders him harmless, this owl knows more than anyone in Hyrule. He will often aid Link in his quest and guide him in the path to defeat evil.
Among the theories revolving around Kaepora Gaebora is the idea that the owl is, in fact, the reincarnation of the Sage of Light, Rauru, or in some other way connected to the Spirit Realm-bound sage, but later on in the game he talks to Link as a child in the Spirit Temple and says that he found it hard to believe that Link could travel in time. In the alternate dimension of Termina, the wise owl has a counter-part known as Kaepola Gaebola, who teaches Link the Song of Soaring.
In Link's Awakening and Four Swords Adventures, an owl similar to the one from OoT helps Link by giving him hints on where to go next.