Migration is a periodic phenomenon exhibited by birds. Waterbirds travel distances of up to thousands of kilometres to reach their wintering or breeding grounds, following mostly fixed flyways. This chapter discusses the major flyways of the world, including the Central American, Central Asian, Pacific, Atlantic, Black Sea, Mediterranean flyways, East Asian–Australasian Flyway, and Mississippi flyway, highlighting their ecological importance for aquatic migrant birds. Flyways can be intracontinental or transboundary, later requiring birds to cross vast oceans to reach their destinations. Stopover sites are refuelling points along the route between the starting point and destination, with wetlands mainly serving as stopover sites. Wetlands provide temporary habitats, food, and resting places. Therefore, wetland conservation is vital to protect migratory birds. Data from various studies confirm that bird populations on major flyways are declining rapidly due to human activities such as habitat loss, poaching, illegal killing, overfishing at stopover sites, and pollution. The routes of the Siberian crane, Northern Pintail, Bar-headed Goose, Blue-throat, and flamingo are shown in this chapter, including several localities in India where these birds arrive. To cope with migration-related challenges, birds undergo many morphological and physiological changes. Morphological features include the shape of the body, wings, feet, and beak, while physiological adaptations include changes in the skeletal system, such as fused pneumatic bones, keel, well-developed flight muscles, and changes in the digestive, sensory, and respiratory systems. This chapter particularly highlights the importance of wetlands, conservation regulations, and their impact on flyways. It emphasizes the need to identify “vulnerable” and “threatened” flyways and to develop appropriate protective measures. The chapter covers the main flyways, the role of wetlands in waterbird conservation, conservation regulations, the need for new cooperative legislation, migratory bird routes, and bird adaptations.