Two Vermilion Birds are painted on either sides of southern entrance in the Great Tomb of Gangseo. The Vermilion Bird is a fictional animal much like the Azure Dragon and is sometimes referred to as Red Bird. According to Shuowen Jiezi (literally “Explaining and Analyzing Characters”, A Chinese dictionary from the Han Dynasty), the Vermilion Bird received its name due to its tendency for soaring into the sky immediately upon seeing flames. Bronze mirrors from the Eastern Han era were inscribed with the phrase, "The Azure Dragon on the left and White Tiger on the right ward off evil spirits, and the Vermilion Bird and Black Tortoise follow the Yin and Yang." Thus, the Vermilion Bird and Black Tortoise represent the Yin and Yang, respectively. According to historical records, the Vermilion Bird originates from the ethereal bird Fenghuang (sometimes referred to as the Chinese Phoenix) and is similar in appearance. Therefore, the Vermilion Bird is often treated as Fenghuang in terms of iconography and symbolism.
A record of particular significance states that "Feng represents the male and Huang represents the female birds." The Fenghuang has been the focus of interest and debate whether it's a hermaphroditic bird or two birds of different genders. Interestingly, the Fenghuang and the Vermilion Bird have been depicted as singular birds as well as in pairs in both Chinese and Koguryo murals.
However, most Koguryo tomb murals depict the Vermilion Bird as two separate entities. The depiction of the Vermilion Bird, which symbolizes the southern cardinal point, as two separate birds may be interpreted as a necessity since southern tomb entrances require that images be painted on both sides of the center. Because the Vermilion Bird is a symbol of Yin and Yang, however, the practice can be interpreted as a way to emphasize balance by painting both male and female birds.
The image shows the Vermilion Birds painted on both sides of the southern entrance at the Great Tomb of Gangseo. The two birds face the entrance as well as each other. They seem ready to flap their wings and soar into the sky. At first glance, the two Vermilion Birds seem to be identical. However, differences in details and the backgrounds are apparent upon closer inspection. Specifically, the differences in the beaks, faces, and overall body lines distinguish the male and female genders. The bird on the left of the entrance is the female, and the male is located to the right.