Tracking study links Manx shearwaters’ small detours to clock mismatch

A new study of Manx shearwaters connects small deviations from their homeward routes with a mismatch between the birds’ internal clocks and local solar time. The finding concerns navigation accuracy, rather than evidence that the adult birds routinely became lost. The research was reported in Science on 29 October. [1][2]

The team used GPS records from 1,045 breeding birds collected over two decades. Oxford’s account describes departures from the expected heading of up to 15 degrees and adults correcting their course. These are tracking-based findings, not direct measurements of a bird’s subjective experience of jet lag. [1]

The proposed mechanism depends on how a sun compass works: the sun’s direction changes through the day, so its position needs to be interpreted against an internal sense of time. Rapid east–west travel can leave that clock out of step with the local sun. Researchers compared predicted compass errors with recorded flight paths; the two followed the expected pattern. [1][2]

Independent interpretation helps explain why a small error need not prevent a bird reaching home. Science News spoke to University of Lucknow chronobiologist Sangeeta Rani, who saw the findings as evidence of birds combining several navigation cues. The reported deviations persisted near familiar coastlines, suggesting coastal information did not simply replace the sun compass. That is an interpretation of the study, not an independent replication. [2]

Taken together, the tracking results and that outside perspective describe a navigation system that can adjust while still showing a clock-related bias. They do not establish that all migrating birds respond identically, or that the same effects apply to inexperienced juveniles. The wider implications remain questions for further research. [1][2]