A study analyzing two decades of GPS tracking data has found that Manx shearwaters experience a form of jet lag during their long-distance migrations across the Atlantic. Researchers at the University of Oxford discovered that when the birds fly eastward across lines of longitude while returning to their breeding colonies on the west coast of the UK, their internal body clocks fall out of sync with local time, causing navigation errors.
The birds rely on the position of the sun as a compass to navigate, with their body clocks helping them track the time of day and adjust their heading accordingly. When rapid eastward travel causes their internal clocks to lag behind local time by up to an hour, the sun appears farther around the sky than their clocks indicate, leading them to drift off course. Adult shearwaters are relatively unaffected by this phenomenon, typically deviating by only about 15 degrees and adding roughly 3 miles to a 600-mile journey. However, younger, less experienced birds attempting their first migration face significantly greater risks.
First-time migrant shearwaters lack the map sense and experience to correct course deviations, making them vulnerable to flying hundreds of miles off track due to sun compass errors. The findings emerged from an examination of 20 years of tracking data and were published in the journal Science. Researchers noted that navigation errors persisted even when birds followed coastlines, where visual landmarks might have provided guidance, reinforcing the central role the sun compass plays in the birds’ directional system.
Experts view the discovery as an important confirmation of how biological rhythms influence animal behavior in wild settings, extending beyond controlled laboratory conditions. The research underscores the broader significance of understanding how internal body clocks affect various aspects of animal function and survival.
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