It'a about a (possibly) magic bird which lives millions of years and learns to live with her captivity. Even though the earth turns old, the bird remains young and has glowing eyes. Birds eyes only glow when they are nocturnal or crepuscular and have light shone in them, so this reference doesn't make any sense. In fact the song was probably, at least partly, written in a bit of drug haze when much meaning is lost.