The Eagle is a nameless character in Spirit: Stallion of the Cimarron. Its gender is male, but is seems to be affiliated with Spirit's Herd, particularly Spirit himself. The eagle is shown to be very attached to Spirit, and searches tirelessly for him when he is taken from the herd. Its is also shown to be playful and competitive, as shown when racing with Spirit, though in the end, Spirit is faster. It is a bald eagle, and is most likly very large, but we will never know its real size. He has no mate, or he would never search for Spirit tirelessly
Without him, we would never understand how fast and wild Spirit really is. He is a major character because it shows how before white invaders came and wrecked all of the land that so obviously belonged to them, the animals lived together in peace, no matter of their species.
He seems to care for Spirit extremely, but he was obviously hurt when he saw Spirit in a new place with horses. He must have felt that Spirit left him and his herd behind, so he turned back. He was very happy when Spirit came back, his trust was in Spirit once again.