Aarakocra

No one really knows how the Aarakocra traveled to Zar'tesk.
Scholars argue that they came by spell jammer ship, some other means of transport or perhaps via the Elemental plain of Air. It is universally agreed that they first appeared in the Kingdom of Shou'tsu.
They have since spread across the realm but tend to stick to small conclaves, when they are not adventuring.  Often used as scouts for their flying ability.