It appears evident that the Rito are in fact the descendents of the worthy Zoras that survived the Great Flood. Supposedly, the Gods changed them so that they could not swim down to ancient Hyrule and yet thrive on. They left Zoras Domain behind and went up Death Mountain. The Zoras shed their scales and were changed into bird people. Thus the Rito were born under the guidance of the great wind spirit, Valoo, from whom their dwelling took its name: Dragon Roost Island.
The average Rito is as tall as a human, with a human-like face dominated by a large, beak (typically raptor-like, but girls seem to have more delicate ones). Their hair and feathers are respectively white (in adult males) and shades of brown, tan sometimes red. Ritos are typically brown skinned, all have red eyes and human-like hands and arms, with their wings looking like baggy sleeves until they need them to fly. When in flight, they have truly majestic eagle wings. Their legs are covered in tough hide, like a bird's, ending in powerful, hooked eagle talons. Given the moderate proportions of the wings, it is assumed that they have hollow bones (allow them to fly still), their talons are however pretty strong for their size. They are able to carry a whole other person their size in their talons and still fly short distances.
Rito are very trustworthy and helpful, never turning down a plea for help, even when in a time of personal distress. Mature Rito grow up to be very formal and polite, not easy to upset (while "chicks" can be very emotive). Should they enter a fight, Rito favor poles, kukris, and of course their own talons.
When a Rito comes of age, they must travel alone up Dragon Roost Island and request a scale from the great Valoo. Although this takes a lot of courage, very few Rito fail to do so, as without this gift they will never grow their wings. It seems that upon receiving their dragon scale, the Rito's hair also changes from brown and white to full white, like an adult bald eagle; but this may not apply to females who seem to never have any white hair.
Rito serve an important function on the Great Sea. Because they can travel quickly and without a boat, they run the Postal Service for the islands. The two lesser deities of wind, Zephos and Cyclos, watch over them while they are away from Valoo and make sure the weather does not harm them (or at least, one of them does).
Until Komali gave it to Link, the Rito royal family were the guardians of Dins Pearl. Also, succeeding an ancient Zora Sage perished at the hands of Ganons monsters, her descendant, the young Rito Medli, took over as the sage of the Earth Temple.
There is some evidence that at least one Hylian had some Rito descendants, which would prove that interbreeding is possible, as one of the Rito Postmasters resembles and is said to descend from a legendary Hylian Postmaster from long before.
It also would seem that some degenerated Rito left their people to become wizzrobes (who would normally be composed of common humanoids), but they are so twisted it is difficult to tell if this is really the case.
Impersonating Ritos seems to be popular among the people who run the flight control platform in the northeast region of the Great Sea.