The route taken by migratory birds and waterfowl when they travel between their breeding grounds and their winter homes. Flyways often follow geographic features such as mountain ranges, rivers, or other bodies of water. Protecting flyways is one of the many responsibilities of wildlife managers. Draining of wetlands, residential and commercial development, and overhunting are some of the factors that threaten flyway sites visited by birds for food and rest during migration. In most cases, international agreements are needed to guarantee protection along the entire length of a flyway. In the United States, flyway protection is financed to a large extent by funds produced through the Migratory Bird Hunting Stamp Act passed by the U.S. Congress in 1934.