The practice of divination, or fortune telling, by interpreting the sound of birds and their behavior; such as, crows in flight or other birds: In the past, it was believed that avimancy was performed when birds, being able to fly in the sky, could commune with the sky god, who was inaccessible to humans.

So all the people who made divinations, or avimancies, with the flight and sound of birds, believed that the birds were messengers whose behavior carried encoded messages or signs sent to people by means of the god of the sky.