According to the legend of Cổ Loa region, when King An Dương Vương built the citadel, every night until morning, the citadel was destroyed by Bach Ke Tinh (white rooster), in the past. Thanks to the help of gods, the king was able to destroy Bach Ke Tinh and build a citadel. Therefore, Cổ Loa villagers abstain from raising white roosters.

According to the story of Mỵ Châu – Trọng Thủy, Triệu Đà brought his army to invade Âu Lạc, when An Dương Vương lost, he brought princess Mỵ Châu with him. Mỵ Châu plucked goose feathers from the shirt Trong Thuy gave her to mark the way. Trong Thuy followed the traces of goose feathers and chased after them. King An Dương Vương ran to the beach along the dead end, he beheaded Mỵ Châu and then the golden turtle took him to the sea. Since then, Cổ Loa people abstain from raising white swan and geese. This custom has faded a lot today.