Right across North America thousands of young ospreys are getting ready to leave the safety of their nest and fly south for the very first time. Why do ospreys migrate? In summer, Martha's Vineyard is the perfect place for ospreys to start life - plenty of nest sites and loads of fish. But as winter approaches the temperature plummets and food dries up. If they don't migrate to where there's more food they'll starve. When its time to go the chicks' parents abandon them - they are now entriely on their own. As the chicks set off they have no idea what lies ahead - they are just following an instinct to head south. But where south? Where will they end up?