"The story of migrating birds is the story of a promise:" "The promise to return." "They fly, often thousands of miles, beset with danger for a single reason:" "To survive." "Their migration is a fight for life." "When spring comes, they take wing for the Arctic." "Some fly relentlessly, night and day." "Others make the trip in stages laboring to reach their distant destination." "To navigate across the latitudes they use the natural beacons of the universe:" "The sun, the stars." "They can track the earth's magnetic field as sensitively as a compass needle." "All over the Northern Hemisphere on every continent the spring migration has begun." "No barriers stop them." "The birds make straight for the far north." "All across America from coast to coast the migrants wing their way towards the Arctic Circle." "Coming from every continent the migrant birds converge upon the Arctic and disperse." "Their life as a community is over." "Now, it's family time." "There is a world apart:" "The realm of sea birds." "Every spring, they quit the ocean waves and flock to nest on the same cliffs and rocks." "The Arctic summer is short-lived." "Soon the northern lands will be locked in the cold of the polar night." "It is time for the fall migration." "No more food." "Time to leave." "Flying south is now a matter of life or death." "Out in the ocean any floating refuge can save the life of an exhausted bird." "For the others, there's no rest until the coast." "ln the fall, there is one prime necessity:" "Stay clear of bad weather." "The fall migration thins the ranks." "Among the survivors, by flying with their elders the youngsters memorize the route and recognize the landmarks they will fly over twice a year, throughout their lives." "For millions of birds from Europe the journey's end is Africa but many will fall by the wayside." "At the end of their odyssey birds from all over reach the heavenly tropics." "Heaven is ephemeral." "It will only last a season." "Once again they must take to the skies in their endless search for food." "No landmass slows the swell of the southern oceans." "Sea birds nest on wind-lashed islands." "The young albatross only comes to land after circling the Antarctic for several years." "A year has passed." "Millions of birds have flown thousands of miles." "ln the sky, the same journeys start over again." "ln the Northern Hemisphere migrating birds herald a new spring." "The promise to return has been fulfilled."