Even bird brains can get to know an entire continent ----- but it takes them a year of migration to do so, suggests a Princeton research team.    The scientists have shown that migration adult sparrows can find their way to their winter nesting grounds even after being thrown off course by thousands of miles.    The team first brought 30 sparrows to Princeton from northern Washington State, where the birds had been in the process of migrating southward from their summer breeding grounds inprefix = st1 /Alaska. Half the birds were juveniles  of about three months in age that had never migrated before, while the other half were adults that had made the round trip to their wintering site in the south-western United States at least once.    After the birds were released, they attempted to resume  their migration, but both age group grew disoriented  quickly.    "All the birds scattered  at first," Wikelski said. "It was clear that they were turned around for a couple of days. But while the adults eventually realized they had to head southwest, the younger birds resumed flying straight southward as though they were still in Washington."    "The adults," said team member Richard Holland, "recovered their bearings because they possess something the younger birds do not, which is an internal map."    "These birds need two things to know where they are and migrate effectively: a 'map' and a 'compass'," saidHolland, a postdoctoral research associate in Wikelski's lab. "What we've found is that juveniles use their compass, but the adults also use their map."    Hollandsaid, "The birds do not lose the compass as they age, but somehow develop the map, eventually applying both tools to keep on track during migratory flights. Scientists already have determined that the compass is based on the sun or the magnetic field, but where the map comes from remains a mystery----one that the team will be exploring in coming years." Where did the 30 sparrows spend their summer?
Princeton Washington Alaska In the southwesternUnited States