As you all know that Flappy Bird was removed from Play Store and iTunes , so here is the way to install Flappy Bird on your Android Device.
Flappy Bird works on Android 2.2+
Download Flappy Bird APK from here - http://www.tusfiles.net/joi1pcmuisdk
Connect your phone to your PC and copy it to your mobile
Go to Settings > Security and check Unknown Sources in your Android phone.
Now Open any File Manager in your phone and open the file (com.dotgears.flappybird) and click on Install , Flappy Bird will be installed.