You don’t need a jet plane to get jet lag – even feathers will do. At least one species of bird gets jet lag, in the sense that its body clock can diverge from local time by more than an hour on fast flights across the Atlantic, as revealed by navigational errors. But it’s exactly the same process that causes jet lag in people,” says Patrick Lewin at the University of Oxford.
Manx shearwaters are small seabirds that fly vast distances, using a technique called dynamic soaring to exploit wind gradients near the sea surface. They breed on islands around the UK and Ireland. While parents are raising a chick, they may fly more than 1000 kilometres westwards to reach rich fishing grounds in the mid-Atlantic.
Once they have food, they fly back in a fairly straight line, diverting only to skirt around landmasses such as Ireland. How do they achieve these navigational feats? While some birds can sense Earth’s magnetic field, Manx shearwaters don’t appear to.
Lewin’s team has confirmed this by attaching small magnets to the birds that should disrupt geomagnetic navigation. Instead, it appears that shearwaters rely on a sun compass – if you know what time it is, you can maintain a course by adjusting your orientation relative to the sun. Many animals, from insects and fish to turtles and birds, have been shown to do this.
If their internal clocks are reset using artificial light and darkness, they head in the wrong direction. For instance, at 6am, a Manx shearwater wanting to fly eastwards back to its nest needs to head sunwards. At noon, it needs to fly at right angles to the sun, which will be due south.
But if a shearwater travels 15° of longitude eastwards, the local time will be 1pm, while its internal clock will still register the time as noon, so the sun will no longer be due south. This means birds flying rapidly east should veer slightly off course in a clockwise direction over the course of day, in the absence of other cues. Other researchers have been attaching GPS trackers to Manx shearwaters for decades, so the paths taken on nearly 4000 foraging trips are known.
Extract — continue reading at the source.
