Finding their way south

At seven on a brisk September morning last year, ecology professor Martin Wikelski piloted a small aircraft tracking white-crowned sparrows through southern New Jersey.

On the ground, postdoctoral researcher Richard Holland and his team followed close behind in two vehicles that looked like something out of a "Star Wars" movie, equipped with antennae and tracking apparatuses.

Now, more than a year later, their research has shed new light on the more sophisticated navigation ability of adult birds. Their findings were published in a recent edition of the Proceedings of the National Academy of Sciences.

The 30 sparrows that were the focus of this particular experiment were "kidnapped" from Seattle while they were in the progress of migrating to their wintering grounds in the southwestern United States. Fifteen were juveniles who had never migrated before, while the others had made the journey to their winter nesting grounds at least once.

Ultimately, the experiment would prove that, while all the sparrows were initially disoriented after their displacement to southern New Jersey, the adults actually corrected their course and headed southwest, while the juveniles continued only to fly south.

The study adds to scientists' understanding of bird migration and could lead to the development of systems that might help people predict and monitor disasters — such as tsunamis or the spread of avian flu — by using birds as sentinels.

"Both adults and juveniles possess an innate compass" that uses the Earth's magnetic field and the sun for orientation, Wikelski said.

Holland added that somehow the adult birds develop an internal "map" that not only helps orient the birds but also corrects for displacement. How adult sparrows actually develop and utilize their map remains unknown.

The team used sparrows, Holland said, because "we needed a bird that migrated on its own and not in a flock as it would be far too difficult to monitor an entire flock," adding that "snow-crowned sparrows have the largest displacement possible on land in the U.S." — a staggering 2,500 miles.

Wikelski and his crew could not track the birds for their entire migration, but unlike most bird migration experiments in the past three decades, they conducted their research in the field rather than in a lab. The entire project took two weeks to complete, which Wikelski said was relatively fast.

Holland said that suspicious police officers were the main hindrance. He was pulled over several times to explain the purpose of the scientific equipment protruding from his tricked-out 1998 Oldsmobile.

Wikelski and Holland said that field research is essential to the collection of migration data. As an added bonus, it is much cheaper than lab research. The success of their project was not due to new data-collection methods — the necessary technology has been around for many years. Rather, they attributed their success to their insistence on gathering data in the birds' natural environment.

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Holland explained that in the early days of biology, scientists conducted field research almost exclusively, but to be dubbed a "proper" science, the focus shifted to experimentation in the lab.

"More information about the 'compass' and 'map' birds use during migration was gathered in this experiment than in the past thirty years," he said.

Wikelski lamented that field research is less common than it once was, noting that he has received financial support from the National Geographic Society and NASA, both of which, he said, "believe in exploration."