However, the story of a piece of rice cake, which is made using a mortar, turning into a white bird is seen in the "Yamashiro-koku Fudoki" (regional gazetteers of Yamashiro Province) and other records, and that implies some sort of a connection to a white bird.
が、碓から生み出される餅が白鳥に変身する話が『山城国風土記』などに見られ、白鳥との関連も伺わせる。