How birds travel thousands of miles every year

Why do animals bother making such long and precarious migratory voyages? Is the lure of an arctic spring feast worth crossing an ocean for?
Wherever you are in the world, you are probably near an animal that has undertaken a remarkable migratory journey, be that a butterfly, bird or sea turtle. But what CrowdScience listener Moses in Kenya wants to know is, why they bother making such long and precarious voyages - and how they're able to reliably navigate over hundreds and sometimes even thousands of miles. In this first of two episodes, presenter Anand Jagatia travels to the Americas to meet the scientists finding and tracking these animals in order to solve the puzzle of where they go and why.