The bluebird traditionally stands for happiness. The phrase "bluebird of happiness" was originally coined by playwright Maurice Maeterlinck in his 1908 play "The Blue Bird" and has since entered the popular lexicon. In the United States, September 24 is National Bluebird of Happiness Day.
In 1908, Belgian playwright Maurice Maeterlinck wrote "The Blue Bird," the story of two children, Tyltyl and Mytyl, who are sent on a magical quest to find the Bluebird of Happiness and save their family. After visiting many fantasy kingdoms, facing Father Time, meeting the spirits of Light and Night, and returning home empty-handed, the children discover that the Bluebird of Happiness is Tyltyl's pet bird and that happiness comes from within.
This was the first time that the bluebird was used to symbolize happiness, but it was not the last. The phrase quickly entered the lexicon, inspiring the state bird of Missouri as well as songs such as the 1934 Radio City Music Hall number "Bluebird of Happiness." This extremely popular song, helped to cement the phrase in popular culture as much as the Maeterlinck play.
On National Bluebird of Happiness Day, gifts that include bluebird imagery are given to wish happiness upon the recipient. The symbolic connection between bluebirds and happiness is not likely to be broken.