Seabirds returning from foraging trips can veer hundreds of miles off course due to a form of jet lag that arises when their biological clocks are out of sync with local time, researchers say. Tracking data from Manx shearwaters off the west coast of the United Kingdom revealed that when the birds returned to their colonies after voyages over the Atlantic, their rapid eastward flights disrupted their sense of time and navigation. The impact was limited on adult shearwaters because the birds were able to correct their orientation in flight. At most, the birds deviated from their course by about 15 degrees. After correcting his course, this added only about 3 miles to a 600 mile trip. But less experienced birds will likely have a harder time, the study found, with first-time foragers risking being diverted hundreds of miles off course. Most studies on bird biological clocks have been carried out under laboratory conditions, but Dr Patrick Lewin, a sensory and behavioral ecologist at the University of Oxford, set out to investigate wild birds with the help of his colleagues. Their analysis of 20 years of GPS tracking data revealed a clear effect when Manx shearwaters flew east across lines of longitude as they returned home, causing their clocks to slow by up to about an hour behind local time. “The bird’s internal clock may be subject to a jet lag phenomenon, which manifests itself when birds veer off course,” Lewin said. Like many animals, shearwaters use the sun as a compass. Because the sun moves across the sky as the Earth rotates, reading its position correctly depends on birds adjusting their course relative to the sun, using their biological clock to keep track of the time of day. Dusk and dawn keep birds’ biological clocks synchronized, helping them adapt to changes in local time. Writing in Science, Lewin said the mismatch between local time and the birds’ internal clocks could cause them to veer off course when the sun is farther in the sky than expected. Surprisingly, the errors persisted when the birds followed the coast, where landmarks could have guided them, further supporting the idea that the sun plays a central role in anchoring their sense of direction. “For adult shearwaters, this delay has a very limited impact on their overall journey, with errors adding 5km calculated to a 1,000km journey,” Lewin said. “However, for birds migrating for the first time, these orientation changes due to sun compass errors could result in deviations of hundreds of kilometers, as they lack a cartographic sense to help them reorient themselves when they get lost.” Professor Richard Holland of Bangor University, who was not involved in the study, said it was a significant finding: “It appears to confirm in wild animals what more controlled experimental studies have shown: the reliance on the sun compass for animals moving during the day, even when it is not accurate.” promotionSubscribe to Down to EarthThe most important stories on the planet. Get all the week’s environmental news – the good, the bad and the gist after the newsletter promo Manx shearwaters spend most of their lives offshore. They cover enormous distances but return each year to islands off the west coast of the UK to breed in burrows. “It is not clear from the study what the consequences of these errors are, since the birds return to their colony and the errors are small,” Holland said. “However, it highlights the importance of understanding the role of biological rhythms in multiple contexts in animal behavior, as we increasingly begin to realize how important they are for numerous biological functions.”
