As impressive as Olympic marathon athlete's performances are, there are examples of even greater endurance seen in birds.  The physical stamina and aerobic efficiency of some birds allows them to migrate up to seven thousand miles one way while their navigational abilities enable them to find specific areas that many have never been to before.  The origin of this seemingly pre-programmed behavior is a mystery.  Or is it?  Uplook Magazine May-June 2005, p.18.  References:  Martin J.  Incredible Creatures that Defy Evolution II.  ExplorationFilms.com;  Tyne J, A.J. Berger.  Fundamentals of Ornithology.  John Wiley & Sons, 1976, pp. 362-363.