Jet lag turns out not to be a purely human complaint. A team led by the University of Oxford reports in Science that Manx shearwaters, ocean-going seabirds that nest on islands around Britain, can fly so fast across longitudes that their body clocks fall behind, and the mismatch shows up as a measurable steering error.
Many birds use the sun to find their way, but that only works if they know what time it is, since the sun moves across the sky during the day. An animal heading quickly east or west crosses into a different solar time faster than its internal rhythm can catch up. Biologists predicted decades ago that this should confuse a sun compass. Proving it on wild animals, as Tim Guilford of Oxford put it, “has seemed impossible until now”.
The proof required patience. Over two decades the researchers fitted 1,045 breeding shearwaters with tiny GPS loggers and picked out 1,837 uninterrupted homeward trips from feeding grounds as far as 1,000 kilometres out. When they compared the routes with what a lagging clock would predict, the match was striking: deviations of up to roughly 15 degrees, with eastbound birds bending clockwise.
The real surprise came near the shore. Even within sight of familiar coastline, the shearwaters kept showing the same small bias, drifting toward land or away from it as the clock error dictated. That suggests they blend the sun compass with landmarks instead of switching one off. For seasoned adults the cost is trivial, a few extra kilometres at most, though young birds on their first migration may struggle more.
Chronobiologist Sangeeta Rani of the University of Lucknow, who was not involved, sees a hidden strength in that flexibility as climate change and construction reshape the landscapes birds rely on.
