Hummingbirds navigate in a variety of ways. The first way involves sunlight. Biologists think that the number of sunlight hours releases in their bodies . When the hummingbird senses a change,it knows that it is time it 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