Endangered seabird shows surprising individual flexibility to adapt to climate change

How animals respond to climate change is key to determining whether populations will persist or disappear. Many species are shifting their ranges as the environment warms, but so far the mechanisms underlying this phenomenon remain unclear. For Europe’s most endangered seabird, the Balearic shearwater (Puffinus mauretanicus), new research has found that individual behavioral flexibility, not evolutionary selection, is driving rapid migration range change of this species.

The study, led by biologists at the University of Oxford, is published in the journal Proceedings of the National Academy of Sciences.

The results could help inform conservation strategies for vulnerable migratory bird species. The results also suggest that individual animals may have greater behavioral flexibility to respond to the impacts of climate change than previously thought, although this behavioral adaptation may have hidden costs, making the long-term impact on this species.

Balearic shearwaters are long-lived, but are critically endangered, mainly due to declining fishing bycatch, as they can be caught on longline hooks and baited gillnets. They breed in remote corners of the Balearic Islands of the Mediterranean, then migrate to spend the summer off the Atlantic coasts of Spain, France and, increasingly, the United Kingdom.

Since 2010, researchers from the Department of Biology at the University of Oxford and the University of Liverpool, as well as collaborators working in Ibiza, have been tracking the colonies of Mallorca using miniature on-board geolocation devices. This revealed that birds increasingly migrate north once they leave the Mediterranean.

It was unclear, however, whether this change was due to individual birds changing their behavior or to natural selection favoring birds that traveled farther.

To answer this question, the researchers compared the migration traces of the same marked individuals over several years. This revealed that individual birds were moving their range north by an average of 25 km per year.

Co-lead author Joe Wynn (Department of Biology, University of Oxford and Vogelwarte Helgoland Avian Research Institute) said: “We found that the best indicator of this change in migratory behavior was average surface temperature. from the sea during the summer. terrains, suggesting that birds may well track changes in underlying marine resources. The fact that people can be so flexible in the face of rapid climate change is encouraging.

But despite this flexibility about where they go in summer, Balearic shearwaters are much more constrained about where they breed, so migrating further north means they have to return further afield in autumn.

Co-author Professor Tim Guilford (Department of Biology, University of Oxford) added: “We found that individuals speed up their return migration as they head north, but this only compensates for partially the extra distance and they still return to the north. Late Mediterranean. We do not yet know how such delays may affect their reproductive success or survival.

This raises the intriguing question of how birds know how far they are from home when they fly back to the colony. To study this, the researchers compared distance estimates from different types of maps that shearwaters might use to guide their migration decisions.

Co-lead author Patrick Lewin (Department of Biology, University of Oxford) said: “We found that the route taken by birds on previous migratory journeys was a much better predictor of return speed than a estimation of the straight line distance to the return point. colony. This suggests that birds do not rely on a large-scale navigation map when migrating, but rather have some memory of the route they took in the past.

“It is possible that memory of individual routes plays an important role in the migration of many other long-lived seabirds, but further research is needed to clarify this,” he added.

Balearic shearwaters belong to one of the most endangered groups of birds in the world and are themselves threatened with extinction as a species. This includes both land-based threats, such as predation by invasive species and habitat degradation, and offshore threats, such as fisheries bycatch, overfishing, pollution and wind farm development. .

Contributor Pep Arcos of SEO/Birdlife said: “In addition to direct threats on land and sea, the growing threat of climate change poses a challenge for a species that breeds in such a restricted habitat. The results of this study suggest that individual flexibility could contribute to distributional shifts caused by climate change outside the breeding season, but it remains an open question what the consequences of climate change might be for birds during breeding. , when their movements are limited by the location of the colony.