Geese were not traditional farm yard animals, so not depicted as often as chickens or ducks. They are migratory birds, which fly away from the shadow (yin), following the sun (yang) to the south in the winter. For this reason they are an embodiment Dao dualism: yin-yang, summer-winter, dark-light & male-female. This would have appealed greatly to the Chinese literati. Geese were also considered a suitable gift for a military man, as their behavioural characteristics – such as the use of sentinels and flying in formation – were not dissimilar to those in the military. Also according to the yili - one of the four writings on Confucian ritual matters - the proper gift to offer a father when requesting a daughters hand was a goose. This custom was probably based on the belief that geese, mated for life making them symbols of marital happiness.