Seabirds racing home over the ocean can get jet-lagged

When you hear the phrase “jet lag,” you probably picture a weary traveler clutching a coffee as the clock on the plane’s screen tells a different story than his body. It turns out that the same disorienting time‑shift plagues a bird that spends most of its life soaring over the North Atlantic. A new study in Science shows that Manx shearwaters—medium‑sized seabirds about the size of a pigeon—experience a subtle but measurable internal clock drift during their long foraging trips, and that drift skews the Sun‑based compass they rely on to find their way home.

What the shearwaters are and why they matter

Manx shearwaters nest in burrows on coastal islands across the North Atlantic, with the bulk of the population breeding around the United Kingdom and Ireland. Roughly half of the birds live in Wales, according to the researchers. They are white underneath, black on top, and possess long wings that enable them to cover hundreds of kilometres a day over open water. Their close relation to albatrosses gives them the stamina to travel anywhere from a few dozen to more than a thousand kilometres in search of food before turning back to their burrows.

Because they spend most of their lives at sea, shearwaters have evolved a sophisticated navigation system. They appear to combine a “map sense”—potentially based on olfactory cues—to gauge their position, with a Sun compass that tells them which direction to fly. The Sun’s apparent motion across the sky, however, demands a reliable internal clock to translate solar position into heading. That clock, the Oxford team discovered, is not perfectly synchronized when the birds cross time zones.

How the researchers tracked the birds

Behavioral and sensory ecologist Patrick Lewin of the University of Oxford led the study. He and his colleagues have been fitting shearwaters with miniature GPS tags since 2004, when the devices first became small enough for a bird of this size. Over two decades they amassed a database of 3,688 foraging trips recorded from 1,045 individual birds. The trips ranged from a single day to two weeks, providing a rich longitudinal record of the birds’ movements.

From that massive dataset the team isolated “homeward flights,” the moments when a bird switches from a wiggly, foraging pattern to a straight‑line sprint back to its colony. The researchers identified the last sunrise the bird experienced—when its internal clock should have matched local time—and then tracked how far east or west the bird traveled thereafter. By comparing the expected Sun‑based heading with the actual GPS track, they could infer whether the bird’s compass was being pulled off course by an internal time shift.

The mechanics of avian jet lag

Birds, like most animals, reset their circadian clock at each dawn and dusk. When a shearwater flies east or west across longitudes between sunrise and sunset, its clock drifts roughly four minutes for every degree of longitude covered. In practical terms, a bird that traverses a thousand kilometres east in a day—about the maximum distance observed in the study—accumulates an internal offset of up to an hour, though most measured shifts were closer to ten or fifteen minutes.

That offset translates into a predictable compass error. If a bird is heading east, its Sun compass will veer clockwise; if it is heading west, the error swings anticlockwise. The Oxford team calculated that the resulting directional bias could reach around fifteen degrees in extreme cases, but the average error for a typical long‑distance flight was roughly seven degrees. In distance terms, that adds only about five kilometres to a thousand‑kilometre trip—a modest penalty for a creature that can cover that ground in a single day.

Evidence that the Sun compass is the culprit

To rule out other potential sources of drift—such as crosswinds, the Coriolis effect, or a magnetic compass—the researchers modeled each factor’s expected influence on the birds’ tracks. None of those models aligned with the observed deviations. By contrast, the pattern of veering matched the predictions derived from the Sun‑compass bias caused by the internal clock drift. Across 335 offshore homeward flights, the birds consistently deviated in the direction the Sun‑based model forecasted.

Although the study was not a controlled experiment—meaning causality cannot be proven beyond doubt—the alignment between predicted Sun‑compass errors and actual flight paths was strong enough for the authors to argue that the jet‑lag effect is the most plausible explanation. The consistency of the bias, even when the birds were far from land, underscores the importance of an accurate internal clock for solar navigation.

How birds compensate for the error

Shearwaters do not rely solely on the Sun compass. The study suggests they maintain a parallel “map sense” that lets them verify their position against a mental map of the ocean and coastline. When the Sun‑derived heading drifts, the bird can detect the discrepancy and make corrective adjustments. This dual‑system approach mirrors findings from earlier work on homing pigeons, which also show a blend of compass and landmark navigation.

Even when the birds follow coastlines—a situation that might seem to reduce reliance on the Sun—the researchers observed a subtle drift toward or away from the shore consistent with the predicted compass bias. That indicates the Sun compass still exerts influence, even when familiar visual cues are available. The authors hypothesize that the balance between the two systems never fully tips to one side; instead, birds constantly weigh compass information against known landmarks, adjusting as needed.

Implications for broader animal navigation

The Oxford findings raise a provocative question: how many other migratory or long‑distance travelers experience similar jet‑lag effects? Any animal that uses a solar compass while crossing time zones could suffer a comparable internal clock mismatch. The authors note that earlier experiments with penguins, which were artificially displaced across longitudes, produced analogous results, suggesting the phenomenon is not limited to shearwaters.

Beyond the academic intrigue, the discovery has practical relevance for bio‑inspired autonomous navigation systems. Engineers looking to emulate avian navigation must account for the fact that a solar compass alone is vulnerable to time‑zone drift. Incorporating a robust internal clock—or a method to recalibrate it on the fly—could be essential for reliable, long‑range guidance in drones or underwater vehicles.

What remains unknown and next steps

While the study convincingly demonstrates a measurable compass bias, it leaves open whether shearwaters suffer the classic physiological symptoms of jet lag—disrupted sleep, altered feeding schedules, or reduced breeding success. Lewin admits that the team has not yet examined how the time shift might affect foraging efficiency or chick survival. Future work will aim to link the clock drift to tangible fitness outcomes, such as the amount of food delivered to the nest or the timing of breeding cycles.

If subsequent research confirms that jet lag imposes a cost beyond a few extra kilometres, it could reshape our understanding of the constraints on seabird foraging ranges and the evolutionary pressures that have honed their navigation. For now, the takeaway is clear: even the most seasoned oceanic traveler can be thrown off by a few minutes of internal time‑error, and that tiny slip leaves a traceable imprint on the bird’s compass. The discovery adds a new layer to the complex picture of animal migration, reminding us that the rhythms of the sun and the ticking of an internal clock are inextricably linked—even for a bird that spends most of its life far from any clock on a wall.

This article was produced with AI-assisted research and editorial support. Reporting is based on the source material cited below. Sources: Ars Technica; arstechnica.com; Global1.News (01 November 2026).

By Jessica Ali, Staff Writer