Ans: This is a sort of challenge to science. Only after studying a lot of animals and birds and doing many experiments, our scientists could put some light on this. Many of the migratory species use the sun as their guiding tool. With the change of the sun's position, while rotating around the earth, the animals or birds trace their path. By using the sun compass, the migratory species make 'time compensation.' Apart from that, the animals or birds that migrate during the night use the star compass similarly. They find a way with the help of North Star, Polaris.