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17 April 2014 12:48 pm ,
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Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
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A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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Birds Follow the Sun
12 January 2001 7:00 pm
Following the sun imperfectly turns out to be the perfect solution for navigation if you're a bird in the Arctic, researchers have found. By using the sun to orient themselves, tundra-breeding shorebirds end up approximating the "great circle routes" used by airplanes and ships--routes that minimize the distance between two points on the surface of a sphere.
Birds can travel thousands of kilometers and arrive at breeding and wintering grounds with pinpoint precision. Fascinated, biologists have investigated this ability for decades. They've learned that birds take their bearings from such things as stars, the sun, landmarks, and Earth's magnetic field. But existing ideas didn't explain why some birds in the Arctic fly east before heading south. So ornithologist Thomas Alerstam of Lund University in Sweden and colleagues used the radar on a Canadian icebreaker in the Northwest Passage to measure the direction of migrating birds flying past.
When Alerstam and his colleagues plotted the routes taken by shorebirds, they found that migrating plovers and sandpipers were curving ever more southward as they flew east. The researchers ruled out other orientation cues and discovered the birds were using a sun compass, they report in the 12 January issue of Science. But the birds' internal clocks can't keep up with their nonstop movement, apparently, and they become out of phase with local time. By failing to compensate for their movement across time zones, they misread the sun's position and veer increasingly southward. But this fortuitous mistake allows the birds to fly south in trajectories approximating the great circle routes that minimize travel distance, saving them valuable energy.
The field study "represents a big leap," says Sidney Gauthreaux of Clemson University in South Carolina, by adding to knowledge gained from lab experiments. He and other ornithologists agree that the uncorrected sun compass strategy works best near the poles, and that additional cues are probably involved at lower latitudes.