Why do birds migrate?

Birds migrate because the best places to live change with the seasons. In northern winters, many insects, seeds, and berries are hard to find, and small bodies spend too much energy staying warm. Flying to warmer feeding grounds can be the better way to survive.

The lovely twist is that many birds travel north for summer because the long bright days help parents find more food for chicks. When daylight shortens, their bodies shift, they fatten up for the trip, and some steer by the sun, stars, and Earth's magnetic field.