”Estas son las mañanitas” is the song the elders in my family sing to us youngins on our birthday. Hear it:
Learn about the song and read the translation: http://gomexico.about.com/od/historyculture/qt/mananitas.htm
Not quite sure why this Mexican birthday song is a tradition in our American-Dominican-Turkish-Jewish-Puerto Rican-Venezuelan-and-who-knows-what-else family but it is!
Interestingly, the song is said to be a morning song sung by dear old King David!