Jet Lag Disorients Returning Manx Shearwaters

Researchers analyzed two decades of GPS tracks from Manx shearwaters breeding on the western UK coast. When birds flew eastward across Atlantic longitudes on their return, their internal clocks lagged behind local solar time, causing a measurable deviation from the optimal heading. The effect was modest for experienced adults but could be severe for first-time foragers.

The Guardian

Manx shearwaters navigate primarily by using the sun as a compass, which requires an accurate sense of the time of day. As Patrick Lewin explained, “To use the sun as a compass you have to know what time of day it is,” — Patrick Lewin, a behavioral ecologist at the University of Oxford. Rapid eastward flights shift the birds into a later time zone, so their circadian rhythm falls behind the sun’s apparent position, producing a “jet lag” mismatch that nudges the flight path off course.

The Guardian

The maximum angular error recorded was seven degrees, adding roughly three miles to a typical 600-mile homeward journey. Lewin estimated that for adult shearwaters the lag translates to about five kilometres extra on a 1,000-kilometre trip, “For adult shearwaters, this lag has very limited impact on their overall journey, with errors adding a calculated 5 km to a 1,000 km journey,” — Patrick Lewin. By contrast, first-time migrants lacking a learned “map sense” could be displaced by hundreds of kilometres, according to Prof. Richard Holland, “However, for first-time migrant birds, such orientation shifts due to sun-compass errors could result in deviations of hundreds of kilometres as they lack a map sense to help reorient them when they lose their way.”

The Guardian

Lewin emphasized that the phenomenon is limited for seasoned birds, noting that adults can correct their bearings during flight. Holland described the finding as confirmation of laboratory work on sun-compass reliance and highlighted the uncertainty about long-term consequences, stating that the errors are small and the birds still reach their colonies. Alice Boyle, a biologist at the Centre for Animals on the Move, praised the study for revealing real-time navigation decisions in wild seabirds, underscoring the broader relevance of GPS-based research.

The Guardian

• “The bird’s internal clock can be subject to a jet lag phenomenon, manifesting as birds flying off course,” — Patrick Lewin, a behavioral ecologist at the University of Oxford

The Guardian

• “For adult shearwaters, this lag has very limited impact on their overall journey, with errors adding a calculated 5km to a 1,000km journey,” — Patrick Lewin, a behavioral ecologist at the University of Oxford

The Guardian

• “However, for first-time migrant birds, such orientation shifts due to sun compass errors could result in deviations of hundreds of kilometres as they lack a map sense to help reorient them when they lose their way.” — Prof. Richard Holland, of Bangor University

The Guardian

• “It’s not clear from the study what the consequences of these errors are, since the birds return to their colony and the errors are small,” — Prof. Richard Holland, of Bangor University

The Guardian