I think you need to consider X and Y distance separately. Also SpeedY. So you'll need 3D array there. Is that how you do it? Cool! Keep up the good work!
I actually got it working now. Each bird has a y speed tag, but they don't move on the x, the pipes do. Therefore I just had to add some code to change the targeted y position each time the pipe passes an x position and the birds try to level out their y with it. Simple stuff! The pipes are sprites, so an array is not needed :)
All this for a simple flappybird game? You might just be better off inventing a new game. Flappy bird is just an easy to pick up... easy to put down game