From D'ni Zoological Society
A species of crow-like bird can be introduced to Relto by way of a Relto page. Only two individuals are ever seen, and they wheel around the island endlessly.
The call is a harsh croak or caw, much like a crow.
The classification of these birds is a mystery: They resemble crows, yet are far more slender; they soar like hawks, yet croak like ravens. It has been theorized that they are a previously unheard-of offshoot of the Corvidae, but their classification is subject to change. Oddly, they rarely, if ever, stop flying, and no one has seen one eat as of yet.