關於盧恩騎士的職業介紹沒提到不能騎
只說可以騎龍
http://i.imgur.com/gaWtT9q.jpg
遊俠也只說可以有狼沒說不能用鳥啊！
盧恩騎士轉職全劇情中也沒有提到任何有關於大嘴鳥的部分
http://ciconia.lofter.com/post/1e0185_efc3d8
反倒是國外網站介紹盧恩騎士有提到
http://ragnarok.wikia.com/wiki/Rune_Knight
以下是節錄 (在background)
No longer could the Rune Knights rideeco Pecosecause ordinary animals are intimidated by Rune Knights' fearsome mana, but the dragons are true creatures of magic and acknowledge the Rune Knights as their masters. Together, the Rune Knights and dragons marched to the front lines of battle to terrorize their enemies.
簡單講就是盧恩魔力強，大嘴鳥這種普通魔物會怕，無法騎乘，所以改騎龍。
不過呢，原始職業設定上到底有沒有這種東西就不清楚了。