Long-distance seabirds navigate with more than a sense of direction. New field evidence shows that their internal sense of time can subtly change the heading they choose.
The ocean has its own version of jet lag
A study published in Science on October 29 reports that Manx shearwaters can make predictable navigation errors when rapid flights across longitude put their internal clocks out of step with local solar time. Researchers led by the University of Oxford analyzed long-term tracking records rather than relying solely on laboratory tests. Their finding does not mean the birds become helplessly lost. Experienced adults often correct their route as they travel, but the pattern reveals how an apparently small timing error can affect the interpretation of the sun. The work offers a rare field test of a mechanism that scientists have long studied in controlled settings.
Twenty years of tracking data
The research drew on approximately two decades of GPS observations from 1,045 Manx shearwaters, covering 3,688 foraging trips. That scale is important because wind, weather and individual behavior can make a single flight difficult to interpret. A large record allows scientists to compare the direction of errors across many journeys and ask whether those errors follow a consistent pattern. The researchers studied birds breeding around the western coasts of Britain and Ireland, where individuals travel far into the Atlantic to feed. The analysis did not involve artificially forcing the birds to take an unfamiliar route; it examined naturally occurring movements.
Why these birds travel so far
Manx shearwaters spend much of their lives at sea, gathering food across a large area while returning to nesting colonies during the breeding season. Some foraging trips take them hundreds of kilometers offshore, and the study describes journeys extending about 1,000 kilometers west of breeding sites. Their return trips can involve rapid eastward travel across many lines of longitude. That movement changes the local solar time the birds encounter even though their internal biological rhythms cannot adjust instantaneously. A journey that looks like ordinary navigation from above may therefore create a subtle mismatch inside the animal.
The sun is a moving compass
The sun is not a fixed point in the sky. Its apparent position changes through the day as Earth rotates, so using it as a directional reference requires an estimate of time. An animal that knows roughly where the sun should be at a given hour can infer a heading. If its clock is slow relative to local solar time, it may interpret the sun as occupying a different position from the one expected. This produces a systematic compass error rather than random wandering. The Oxford researchers tested whether real shearwater tracks showed the direction of error predicted by this timing mechanism.
What happens on eastward flights
When a shearwater flies rapidly east, it reaches longitudes where sunrise occurs earlier. Its body clock may still be calibrated to the more westerly position it recently occupied. The study suggests the lag can reach roughly an hour. With the bird’s time estimate behind local solar time, the sun appears farther around the sky than its internal reference predicts. The resulting heading error tends to be clockwise on the return trips studied. This is a specific, testable prediction: the direction and approximate size of the deviation can be compared with actual GPS tracks.
How the researchers tested competing explanations
Birds can use more than one navigation cue, including the Earth’s magnetic field, celestial information and familiar landmarks. The scientists therefore compared the observed flight deviations with models based on a shifted sun compass and an alternative explanation involving magnetic conditions. The sun-compass account fit the data better, according to the University of Oxford’s research summary. That comparison is stronger than simply noting that a bird turned after crossing longitude. It links the direction of the turn to a mechanism with an independently predictable effect. Still, observational evidence does not reveal every sensory decision the bird makes in flight.
A coastline did not eliminate the error
One striking result was that deviations persisted even when birds flew near visible coastlines. A simple assumption might be that landmarks would immediately override an inaccurate sun compass. Instead, the researchers found that birds tended to fly closer to shore when the predicted error pointed landward and farther out when it pointed seaward. That pattern suggests the sun remained influential even where other cues were available. It does not imply that shearwaters are unable to recognize a coastline. Rather, different sources of information may contribute to navigation in ways that are not instantly or perfectly reconciled.
The errors were usually modest
In the tracked adult birds, deviations reached roughly 15 degrees. The researchers estimated that a bird returning from 1,000 kilometers away with an average seven-degree compass error, while continually correcting its route, would travel only around five additional kilometers to reach the vicinity of its colony. That calculation is an illustration, not a claim that every bird traveled precisely five extra kilometers. The distinction is important because headlines about jet lag can make the problem sound catastrophic. For experienced shearwaters, the measured effect appears detectable but often manageable.
Why young migrants might face greater risks
A first-time migrant may not possess the same learned map or experience as an adult returning to a familiar colony. If a compass error persists without reliable opportunities for correction, small deviations could accumulate over a much longer journey. The researchers suggest that this might shift a young bird’s eventual position by hundreds of kilometers. That is a possible consequence, not a demonstrated outcome for the tracked Manx shearwaters. The study focused on foraging trips and the navigation patterns of birds that could often correct their course. Testing the implications for inexperienced migrants remains a separate research challenge.
The difference between orientation and navigation
Orientation means choosing a direction; navigation also involves knowing or estimating where one is relative to a destination. A sun compass can provide a heading without necessarily supplying a complete map. An experienced seabird may combine directional information with knowledge gained from prior journeys, environmental cues or repeated course corrections. This distinction helps explain how a measurable compass error can coexist with successful returns to a breeding colony. The Oxford findings illuminate one part of a larger navigation system. They do not reduce the birds’ impressive journeys to a single biological clock.
What the results reveal about circadian rhythms
Circadian clocks coordinate many processes across roughly 24-hour cycles. Light exposure helps synchronize those clocks with the external day. In humans, crossing time zones can cause fatigue and disturbed sleep while the body adjusts. The shearwater study identifies a comparable mismatch between internal timing and local solar time, but its measured consequence was a navigation error. Researchers have not shown that the birds experience human-like symptoms such as exhaustion or insomnia. The biological similarity is interesting precisely because it permits new questions without assuming identical subjective experiences across species.
Why GPS data matter for animal cognition
Many questions about how animals perceive the world are difficult to answer without disrupting natural behavior. GPS tracking offers an indirect method: researchers can derive predictions from a proposed cognitive mechanism and look for its signature in thousands of movements. The approach depends on careful statistical modeling and awareness of confounding factors such as wind and geography. It cannot directly record a bird’s internal thoughts, but it can test whether the animal behaves as though it is using a particular cue. The shearwater research demonstrates how long-running field datasets can reveal processes that are otherwise hard to observe.
Conservation implications remain uncertain
Seabirds face threats including changing prey distributions, fisheries interactions and environmental disturbance. It is tempting to add jet lag immediately to that list, but the new study does not quantify a population-level survival effect. Adult birds in the analysis generally retained the ability to reach home. Future research could examine whether navigation errors become more consequential during extreme weather, unfamiliar routes or long migrations. It could also investigate whether changing environmental light cues alter the birds’ ability to reset their clocks. Those are worthwhile questions, but the October 29 results do not yet answer them.
What scientists will investigate next
Researchers want to know whether clock mismatches affect other behaviors beyond heading choice, how quickly different species recalibrate and whether inexperienced animals face larger costs. Experimental work could complement field tracking by measuring timing changes more directly, while further GPS studies could compare migrations across regions. The strongest conclusion today is narrower: natural longitudinal travel was associated with predictable deviations consistent with a lagging sun compass. The finding adds an important piece to the puzzle of animal navigation and gives researchers a way to test how internal timekeeping influences movement in the wild.
Frequently asked questions
How many birds were studied?
Researchers analyzed GPS records from 1,045 Manx shearwaters across 3,688 foraging trips over approximately 20 years.
Do seabirds become lost because of jet lag?
Experienced birds in this study generally corrected their course. The observed compass deviations were modest, reaching about 15 degrees.
Is the sun the only navigation cue?
No. Birds can use magnetic and environmental information too, but the sun-compass explanation best matched the reported pattern.
Source: University of Oxford research release, October 29, 2026. Research paper: Science DOI 10.1126/science.adz2542.
