Manx shearwaters may experience a form of jet lag when flying rapidly back to their breeding colonies, according to a study published October 29 in Science. The shift in their internal clocks appears to interfere with their ability to use the sun as a compass, leading them to veer slightly off course.
Researchers examined 20 years of GPS records from 1,045 wild breeding shearwaters. The birds made 3,688 journeys between breeding and feeding grounds; the team focused on 1,837 eastward trips back to the colonies. As predicted, the data showed that the birds’ routes deviated clockwise by as much as 15 degrees.
Manx shearwaters forage in the Irish Sea and northeast Atlantic, sometimes traveling more than 600 miles from their breeding islands. On their return flights, they navigate partly by the sun’s position. Because the sun’s apparent position changes through the day, using it as a compass requires birds to know the time—information their internal clocks help provide.
The researchers considered other possible explanations for the route deviations, including crosswinds and distance from the colony. The sun-compass effect was the factor that best predicted the observed changes in orientation, lead author Patrick Lewin, an ecologist at the University of Oxford, told New Scientist.
The birds also continued to veer off course while flying alongside coastlines. The finding suggests that they use several navigation cues, even when those cues may point in different directions. The study’s authors estimate that a seven-degree compass error would add about three miles to a journey of roughly 620 miles, a small detour relative to the full trip.
The research examined only Manx shearwaters. The authors suggest that other long-distance travelers, including some birds, bats and insects, could also experience similar clock shifts, but further research is needed. They say the next step is to determine whether the effect alters the birds’ behavior or has physiological consequences.
Sources: Smithsonian Magazine.