---
title: "The Shearwater’s Slipping Clock: Seabirds Flying Home Get Jet Lag, and It Bends Their Compass"
description: "Twenty years of GPS tracks from Welsh and British colonies show that fast east–west flights throw off the birds’ Sun compass"
author: "Jan Sokol"
published: 2026-10-31T11:15:26Z
modified: 2026-11-01T01:09:15Z
url: https://rews.cc/a/the-shearwater-s-slipping-clock-seabirds-flying-home-get-jet-0211d0
language: en
tags: ["biology", "navigation", "birds", "clocks", "science"]
publisher: "Rews (https://rews.cc)"
---

# The Shearwater’s Slipping Clock: Seabirds Flying Home Get Jet Lag, and It Bends Their Compass

*Twenty years of GPS tracks from Welsh and British colonies show that fast east–west flights throw off the birds’ Sun compass*

By Jan Sokol · October 31, 2026 · https://rews.cc/a/the-shearwater-s-slipping-clock-seabirds-flying-home-get-jet-0211d0

## In brief

- A study published October 29 in Science finds Manx shearwaters get jet lag on fast east–west flights home from feeding grounds
- The birds reset their internal clocks at dawn and dusk, so each degree of longitude flown puts them four minutes out of sync
- Oxford researchers analysed GPS tracks from 3,688 foraging trips by 1,045 birds, collected since 2004
- On 335 homing flights out of sight of land, deviations matched Sun-compass predictions better than wind, Coriolis or magnetic causes
- Errors reached about 15 degrees, but birds that keep correcting add only about 5 km to a 1,000 km eastward day

At every dusk and every dawn, somewhere over the North Atlantic, a bird about the size of a pigeon resets its clock. Between those two moments it has the Sun to steer by, and the Sun keeps moving. The bird is the Manx shearwater. A study published on October 29 in *Science* finds that its reliance on the Sun has a price. If it flies far enough east or west in a single day, its sense of the hour slips, and its compass slips along with it. Seabirds, it turns out, get jet lag.

The lead author, [Jacek Krywko reported for *Ars Technica*](https://arstechnica.com/science/2026/10/seabirds-racing-home-over-the-ocean-can-get-jet-lagged/), is Patrick Lewin, a behavioural and sensory ecologist at the University of Oxford. The paper’s title, according to the [press release issued through EurekAlert](https://www.eurekalert.org/news-releases/1149106), states the finding in the journal’s plain way: “Rapid longitudinal flights cause time shifts and sun compass error.”

## A bird of burrows

Lewin describes the shearwater as white below, black above and very long in the wing, a close relative of the albatross. It nests in burrows on coastal islands around the North Atlantic. Most of the population breeds around Britain and Ireland, and about half of it lives in Wales. The birds go out to feed anywhere from a few dozen to more than 1,000 kilometres into the ocean. While one partner sits on the egg, the other goes out to sea, and once it has fed, Lewin [told NPR](https://www.npr.org/2026/10/29/nx-s1-6019228/manx-shearwater-jet-lag-birds), “they absolutely bomb it back to their colony”.

Researchers think the way home is found in two steps. First the bird works out where it is with some kind of map sense, possibly based on smell. Then it uses the Sun to set its heading.

## A compass that keeps moving

The trouble is that the Sun does not stay put. Lewin explains it with a traveller heading south:

![A seabird with outstretched wings glides over a textured blue ocean beneath three orange suns and pastel clouds, casting a long shadow across the waves.](https://rews.cc/img/829c144a8c85894a3f2dd6f7dce5342a3e7076dc.webp)

> “At sunrise, when the Sun’s in the east, it needs to be traveling 90 degrees clockwise of the Sun, but by midday it needs to be traveling straight towards the Sun, and by sunset it needs to be traveling 90 degrees anticlockwise of the Sun.”

So steering by the Sun means knowing the time. Here is a thought, offered as reflection and nothing more: anyone who takes their bearings from a single great authority in the sky also has to know the hour, because that authority never stands still.

The shearwater does carry an internal clock, as nearly all animals do, but the clock is imperfect. It recalibrates only at dawn and dusk. For every degree of longitude the bird covers between sunrise and sunset, the clock drifts four minutes away from local time. Flying east, the bird misjudges where the Sun should be and veers clockwise. Flying west, it veers anticlockwise.

## Twenty years of tracks

Scientists had seen something similar before, in penguins that were caught and quickly moved across lines of longitude. Nobody had clearly shown it in wild animals travelling on their own, because the effect is small and only shows up in a large amount of data. Testing it in the wild, Tim Guilford said in the release, “has seemed impossible until now.”

The data already existed. Guilford, who supervises Lewin at Oxford, and Chris Perrins, a long-time Oxford shearwater researcher, began fitting the birds with GPS tags in 2004, the first year the devices were small enough for a bird this size. Twenty years later the team had tracks from 3,688 foraging trips, made by 1,045 birds from colonies along Britain’s western coasts. The trips lasted anywhere from a day to two weeks.

The homeward legs were easy to pick out. While foraging, the birds make short, wandering flights between dives. When they decide to go home, Lewin said, they switch to flying “as fast as they can in pretty much a straight line continuously without stopping for really long periods.”

![A tangled coral path across a textured teal sea straightens into a line leading to a rocky island in the upper right.](https://rews.cc/img/d913a0232c01597a2a88893930826b53cad8fba0.webp)

For each flight home, the researchers found where the bird had last seen the sunrise, the moment its clock should have matched local time. At every GPS fix after that, they calculated how far east or west it had gone and how much that should have bent its Sun compass. Each bird was heading for one known burrow, so the predictions could be checked against how the birds actually strayed.

The time shifts were tiny. “About an hour is pretty much the maximum that we observed. Most of these are probably 15-minute, 10-minute time differences,” Lewin said. “For us, that would be pretty imperceptible, but it does still have an effect on their compass orientation that we can detect.”

On 335 homing flights made out of sight of land, the birds veered the way the Sun-compass predictions said they would. Lewin is careful about causation, because this was not a controlled experiment. Still, the team worked out the errors that crosswinds, the Coriolis effect or a magnetic compass would produce, and none of them fit the data well. “Our observed biases match by far the best to the Sun compass biases that we would expect,” he said.

## The small cost of error

The errors reached up to around 15 degrees. That sounds large, but it cost the birds little, because a bird with a map sense can check where it is, notice the drift and correct. The team calculated that for a shearwater flying 1,000 kilometres east in a day, about the most they observed, the average error would be roughly seven degrees. A bird that keeps checking its position adds only five kilometres to the trip. NPR gave the figure as about three miles on a 600-mile journey.

Fifteen degrees at most. Five extra kilometres on a long day. The ocean forgives that much.

![A vintage-style compass with coral and navy needles floats among choppy teal ocean waves and cream-colored foam.](https://rews.cc/img/b6e2610844afbdf0ed16b35959784d74e0e593e2.webp)

## Two ways of knowing

The bias also showed up along the shore. When shearwaters followed a coastline, they still drifted slightly closer to it or farther from it depending on their predicted compass error. Two decades ago, work at Oxford found that homing pigeons with shifted clocks did the same thing even while following a familiar road. That led researchers to suggest that birds may run two navigation systems side by side, one built on the compass and one on familiar landmarks, with neither ever fully taking over.

Lewin offers another possibility: a bird may not know exactly where on the coast it is, and may use the Sun to decide which way to follow it. “We don’t quite know. And I think it’s an interesting question, especially as people try and design bio-inspired autonomous navigation systems,” he said.

## What the night does to them

The study could not say whether the birds suffer the other miseries of jet lag, such as broken sleep or hunger at odd hours. “We’ve not been able to investigate that yet,” Lewin said. The team’s next questions are whether the time shifts affect when the birds forage, how much food they bring home, and how well they breed.

Lewin thinks other animals quite likely get jet lag too. Any creature with an internal clock that travels far enough east or west in a day could be affected, which mostly means flying animals and those living near the poles, where lines of longitude run close together. The long-term aim is to learn whether animals that live with constant jet lag have evolved ways to cope with it.

“In humans, if you do it a lot, in the long term it has really negative health impacts,” Lewin said. “So maybe we could take some inspiration from these animals that are constantly experiencing jet lag and see if there are ways that we can mitigate jet lag affecting humans.”