The waste has long been fascinated with the flight-given among their numbers, particularly members of avian races such as the common corvus or the elegant and deadly scissor hawk. Other smaller species-insignifcant members of the sky dazzle the knuckle-draggers of the world below with their fluid formation movements, flying in flocks through the dusty sky.
After many a dude ate many an avian, and began to wonder how much of the flying monster was truly edible and possibly tasty, they started to pay more attention to how the animals came apart when being prepared. Although dismissed at the time, near the bottom-back of the brain, just under the eye cavity, a small grey "stone" was found, two in each bird under each eye near the brain.
It wasn't until many moons after that a curious scribe in an organized research institution began to examine them more, and found how responsive the stones were to the presence of a electromagnetic force.
A very delicate operation on a domestic stock of avians (that succeeded after the 8th attempt) succeeded in removing both of the stones through the bottom of the eye. The subject was then released, where it displayed trouble flying and appeared dazed & confused. The conclusion as made that the stones electric signals were necessary to determine body position. That, or the subject suffered ocular destruction/brain damage from the invasive removal.
After counsel with a few more advanced thinkers, it was believed the "stones" were used to calculate movement. This was the first link made as the purpose of the bird-stones, now known as an "avistone".
More dissections led to the discovery that many other species of birds also had similarly sized stones at varying positions in the head, assumed to be signaling movement.
Believing at first there may be a massive, electric magnetic core somewhere controlling the avian population, the original research was stopped from making a foolhardy journey to find that core when another researcher presented evidence that the Avantsphere itself generates a weak but ever-present magnetic field.
The body of research these early realizations led to, a small field known as avionics, worked to understand the relation of avistones to the movement patterns of birds.
It was concluded that avistones assist the wielder in determining position relative to their location on the Avantsphere, and the connection to the electromagnetic field links the locations of all other avians [of a certain species] present. Thus, the resounding conclusion made was that avian's fantastic flight patterns come as the result of instant signals sent through the Sphere's electromagnetic wave, guiding group movement between species.
In a common dude's summary: birds got these funny rocks in their heads that tell them where other birds are because of magiks, and the birds all fly pretty together because of that.
Any testing by dude hosts has proved fruitless thus far, and the avistones have yet to find a use outside of their current skyward users.