Poor little bird, all he wants is some seed. In Bird Strike, you must guide Gerald as he uses the power of rockets to launch himself further and further into the atmosphere, but what goes up must eventually come down.
To initially launch Gerald off his perch you pull back the power lines. After that, it's a simple affair of tilting the iphone to move Gerald left and right, avoiding obstacles, and collecting seed. When Gerald reaches a certain height, a UFO will zap him, sending him crashing to the ground turning the game on its head as you smash through all the obstacles you avoided on the way up.