One of the scene that left an impact from the BBC documentary movie, Earth, is the migratory birds traveling thousands of miles and flying over the highest mountain range in the world - the Himalayas. They flew from the north east to India to escape the harsh winter.
They have to soar to great heights and overcome the chilling wind turbulence to cross the mountain range. To see them flapping their winds with every once of strength in their body against the wind is moving. Here we are talking about endurance and determination of the birds that great athletes possess. In fact such admirable qualities are found in all migratory animals. They travel long distant without food or water, overcoming harsh terrains through sheer determination and survival instinct. Their will to survive is so strong it put us human to shame.
They did it long before man boast of his conquest of Mt Everest. They do it naturally, without training, external warm clothing, compasses and tons of equipment to help them.
They just do it from instinct. Talk about the marvel of Nature.