National Geographic: Planet of the Birds

Birds survive in almost every habitat across the world. From the North Pole to isolated islands off the coasts, these resilient animals can live almost anywhere. How do birds thrive in such different environments? They have adapted to be tough and versatile. It's their feathers, the way they move, the way they sing. For birds, variety is not only the spice of life, it's the reason for life. They are the nomads of the sky.