Divination by birds was a public institution before it was a dream convention. Roman augurs took the auspices, literally the bird watching, before acts of state, reading flight, cry and feeding; Greek seers read omens from eagles and herons, and the practice runs through Etruscan, Germanic and Arabian tradition alike. The bird as message bearer is equally old, doves returning to the ark with the olive leaf, Odin's ravens Huginn and Muninn flying out over the world each day and returning with news. When a dream dictionary reads a bird toward tidings, it is compressing that history.
The soul bird is the second great register: Egyptian art shows the ba, the personal soul, as a human headed bird leaving the body, and the bird released or escaping at death recurs in folk and religious imagery across cultures. Flight upward from the earthbound made birds the natural figure of spirit, aspiration and the part of a person that is not held down.
The psychological traditions inherit both registers. The Jungian line reads dream birds toward thoughts and the winged, transcendent function of the psyche, with the bird's kind setting the tone, raven and dove being nearly opposite dreams. The handbooks always read by species too, owls toward warning, doves toward peace, birds of prey toward power or threat, and modern interpreters keep the habit, weighing kind, flight and song before anything else.