When a bird flying in the air takes a left turn, it tilts its body in a way that the air around the bird offers a dragging force in left direction, perpendicular to initial direction of motion. The horizontal component of the normal force balances the wings of the bird as a result the bird doesn’t fall and gets proper centripetal force. Here, the Newton’s Third law of motion comes into picture, the air underneath also exerts equal and opposite force on the bird. Thus, it gets balanced due to centripetal force which is provided by the horizontal component of the normal reaction.