Why do birds fly south for the winter?

Birds migrate—or move regularly from one place to another—for several reasons, including warmth and the availability of food and water. Many species of birds mate and nest in specific areas of the world. Most of these areas are only comfortable during the warmer months of the year, so when the cold weather arrives birds migrate to warmer climates. These trips can be as long as thousands of miles. For example, the American golden plover breeds north of Canada and Alaska during the Northern Hemisphere’s spring and summer. In the Northern Hemisphere’s fall, the plovers travel to southeastern South America to spend the “winter”—which is the summer season in the Southern Hemisphere—allowing the birds to find plenty of food. When spring arrives again in the Northern Hemisphere, the trip is reversed, and the plovers migrate back to the northern nesting grounds to breed.