The Ibis was a bird particularly sacred to the ancient Egyptians. Being a hearts shaped it represented the heart under the protection of Thoth/Hermes, the god of wisdom learning and writing. When fleeing from the giant Typhon Hermes changed himself into an Ibis. This bird is also sacred to Isis, symbolizing the moon as the hawk symbolizes the sun. The moon god Aah is also sometimes seen as having the head of Ibis. The white Ibis appears in Lower Egypt during the time when inundation of the Nile takes place, making it especially sacred.
John and Caitlin Matthews, The Element Encyclopaedia of Magical Creatures, 2013, Ibis, p 251