The original version of Flappy Bird is not available on Android. The game was removed from both Google Play and the App store on February 10, 2014. Unofficial versions of the game are available on Android, but they are attempts to replicate tie original game.
The only official release of the game available is called Flappy Birds Family, which is a revised version of the original game. Flappy Birds Family is available only for Amazon Fire TV. The only way to obtain the original game is to buy a phone with the original 2013 app pre-installed. Because of high demand, these phones can be very expensive.