As the season grows colder and food supply diminishes, birds withdraw southward where food is easier to obtain. In the fall, more than 350 species of birds leave for Mexico, the Caribbean, Central and South America, traveling thousands of miles to their winter homes. They may travel hundreds of miles in a day or great distances in carefully organized flocks. Many species travel by night and may fly non-stop over large bodies of water such as the Gulf of Mexico. Birds will readily accept suet , a fresh source of water and a backyard feeder full of bird seed as they make their long journeys.
Birds migrate through aerial corridors called flyways.
There are various theories explaining how flocks of migrating birds find their way across long distances. Different species may use different environmental clues such as the stars, the earth's magnetic field, the sun or landmarks such as rivers, mountain ranges or seacoasts. Birds not only migrate from North to South and back, but also between East and West and mountains and plains. Birds will follow the course of a season's flower crop or insect hatches. Banding has proven that some birds will visit the same backyard year after year.