Behind Journey of the Emperor –

The Vermilion bird is one of the Four Symbols of the Chinese constellations. According to Wu Xing, the Taoist five-elemental system, it represents the fire-element, the direction south, and the season summer correspondingly. Thus it is sometimes called the Vermilion bird of the South. 

It is often mistaken for the Fenghuang due to similarities in appearance, but the two are different creatures. The Fenghuang (similar to the phoenix in western mythologies) is a legendary ruler of birds who is associated with the Chinese Empress in the same way the dragon is associated with the Emperor, while the Vermilion Bird is a mythological spirit creature of the Chinese constellations.