The nightingales warned her and foreshadowed Occtis being in mortal danger.

Well, nightingales are harbingers of death, Thaisha was trying to hear the falcon's cry but got little nightingale instead. Wild shaped and went to get Occtis.

Not only that but that group is essentially inside the administration; Azune is a "cop", Bolaire and Hal are the art and culture people and Murray is a professor. If any of them leaves, it gives away that they KNOW and they'll be swiftly dealt with.