Eagle is a universal symbol. It’s broad wings, a powerful beak, talons, a fast flight and an extremely keen eyesight had impressed, excited human imagination. That’s how it became a subject of a very rich symbolism. Being the king of birds it is a messenger of the Sun because it can look at this celestial fire without any fear. In the Biblical tradition eagles symbolise angels.
It is a symbol of contemplation as well and is identified with Saint John and his Gospel, thus, present in Tetramorph (a symbolic arrangement of four differing elements, other elements are Matthew, the winged man; Mark, the lion; Luke, the ox). It brings souls to God on it’s wings.
In Greek mythology eagle is a patron bird of Zeus. In Roman symbolism it was a sign of Empire, that’s why it represented Christ during the Middle Ages: his ascension and royalty. Eagle (simple or double-headed) is present in many coat of arms of different countries or towns all over the world.
Eagle can become young again: it exposes himself to the Sun and when his feathers start to burn, it dives to a pure water. It could be compared with the passage through fire and water in Alchemy.The duality of eagle and snake mean Sky and Earth or the perpetual fight between angel and demon.