Usually a specific Angry Bird will perform better in certain level. Learn their powers and advantages and choose the bird that is best suited. After you have started a level with a specific bird, you cannot switch until you restart or the current bird runs out of attempts. Some levels may require that you have your birds work together. For example, sacrifice one (such as Bomb) to destroy large obstacles and clear the way for the next bird. Although each turn places random obstacles on the map, they ones you start with are usually worse.