Migration is a seasonal movement of birds between their breeding and wintering grounds. This movement is driven by both internal and external cues, such as the need to escape harsh conditions, locate food sources, and find nesting locations. The migration period is physiologically challenging for migrants as they encounter fluctuating temperatures, humidity, oxygen levels, air pressure, and pathogenic stress while crossing different types of landscapes. This chapter includes information about various types of migration, the process of migration, migratory costs, Preparation for migration, and morphological and physiological adaptations of birds to cope with challenges in detail. Morphological adaptations include changes in body size/shape, changes in feathers, and changes in wing morphology that influence the flapping, gliding, and soaring during migration. Efficient metabolism and energy conservation are achieved by increasing the storage of fat before migration and dynamic soaring. Muscle mass shows changes before, during, and after migration. Physiological adaptations, such as shrinkage of the digestive system, an improved innate immune system, osmotic balance by salt glands, changes in the respiratory system for efficient oxygen supply in hypoxic terrain, increased circulation to the heart and muscles, increased antioxidant production, and navigation-related structures and mechanisms, are discussed in detail concerning seabirds. This chapter also includes navigation and orientation-related adaptations that include homing through the use of celestial bodies, magnetic field detection by magneto-receptors, navigation by landmarks, and infrasound in detail.