Aiwendil

A Maia who dwelt in Valinor, and apparently one of the people of Yavanna Kementári, the Queen of the Earth. The name Aiwendil means 'lover of birds', so (as we might expect from his connection with Yavanna) even in his earlier life he was closely associated with the creatures of nature.

During the earlier Third Age, when Sauron's power was beginning to reappear in Middle-earth, the Valar elected to send a series of emissaries across the Great Sea to aid the people of the Mortal lands in their struggle against the Dark Lord. The first of these to step forward was Curumo (who would become known as Saruman in Middle-earth), but it seems that Yavanna had decided to send her own representative. She prevailed upon Curumo to take Aiwendil across the Sea with him (it seems that Curumo was unwilling, but was obliged to comply with Yavanna's wishes).

In Middle-earth Aiwendil acquired a new name, becoming known as the Wizard Radagast the Brown. Just as in Aman, he maintained the friendship of living things, but it seems that this distracted him somewhat from his mission of aiding Elves and Men. Nonetheless, he remained on good terms with Gandalf and the Wise, though Saruman held him in contempt.

It's unclear whether Radagast was able to return to his former existence as Aiwendil after the final Fall of Sauron. Certainly, he did not sail back on the White Ship with Gandalf and the Three Keepers; he may perhaps have found other means to cross on his own, or he may have remained in Middle-earth among the birds that he loved.