Jet lag shifts Manx shearwaters off course

Manx shearwaters can become temporarily disoriented when fast eastward flights leave their internal clocks behind local solar time, causing predictable errors in their sun-based navigation, researchers report. The deviations were modest for tracked adults, but the researchers say inexperienced birds could be more vulnerable because they may be less able to correct their course. The study, published in Science, analysed two decades of GPS tracking data from Manx shearwaters returning from foraging trips over the Atlantic. Researchers compared the birds’ observed flight directions with predictions based on how their internal clocks would lag after travelling east across lines of longitude. The tracks showed deviations consistent with birds misreading the sun’s position. Manx shearwaters use the sun as a compass, a system that depends on knowing the time of day because the sun appears to move across the sky. Researchers estimated that rapid eastward returns could leave a bird’s internal clock up to about an hour behind local solar time. That mismatch can make the sun appear to be in a different position than the bird’s clock predicts, shifting its heading. For adult birds, the...