Hummingbirds Hummingbirds navigate in a variety of ways. The first way involves sunlight. Biologists think that the number of sunlight hours releases hormones in their bodies. When the hummingbird senses a change, it knows that it is time to migrate and fly away. A second reason relates to gravity. When the hummingbird starts to fly south (or return north), it uses the Earth's gravity to sense direction. In other words, the hummingbird's body can feel the pull of gravity, just like a sailor's compass. Hence it knows if it is flying north, south,east or west.