Why would my ex boyfriend text message me a “Happy Birthday” message after more than a year of being broken up

My four year relationship ended because he was a cheating lying drunk on the 2nd of May 2007. It was a no communication break up which is what I wanted. He was with the girl he cheated on me with and to my knowledge he still is with her, but I hear he is pretty miserable. The last time I saw or spoke to him was at the bar the night before Thanksgiving, and that was like “Hey, how ya doing” and that was it. Well flashforward to August 4th 2008 and he text messaged me “I Just wanted to wish you a happy birthday” then it that dumb little verizon animation thing winking. What the heck was his motive here? I do not want him back in my life, he is tragic. However, the text has got me thinking WTF?