2024-02-02 13:12:10
MADRID, 2 Feb. (EUROPA PRESS) –
Flexible individual behavior and not evolutionary selection is behind the rapid change in migratory range due to warming of the most endangered European seabird, the Balearic shearwater.
This finding from a new ten-year study led by the Oxford University could help inform conservation strategies for vulnerable migratory bird species.
How individual animals respond to climate change is key to determining whether populations will persist or become extinct. Many species are changing their ranges as the environment warms, but until now the underlying mechanisms have been unclear.
The results of the new study also suggest that individual animals may have greater behavioral flexibility in responding to the impacts of climate change than previously thought, although this behavioral adaptation may have hidden costs, making the impact a long term in this species is not clear.
Balearic shearwaters are long-lived but critically endangered, mainly due to declines caused by bycatch in fisheries, as they can become entangled in baited longline hooks and gillnets. They breed in remote corners of the Balearic Islands and then migrate to spend the summer off the Atlantic coasts of Spain, France and, increasingly, the United Kingdom.
Since 2010, researchers from the Oxford Navigation Group (part of the Department of Biology at the University of Oxford) and the University of Liverpool, together with collaborators working in Ibiza, have been tracking colonies in Mallorca using miniature onboard geolocation devices. This revealed that the birds They have been migrating further north once they leave the Mediterranean.
However, it was unknown whether this change was being driven by individual birds altering their behavior or by natural selection favoring birds that traveled farther.
To answer this, the researchers compared the migratory trajectories of the same tagged individuals over several years. This revealed that Individual birds were shifting their range northward by an average of 25 kilometers per year.
Co-lead author Joe Wynn, from the Department of Biology, said in a statement: “We found that the best predictor of this change in migratory behavior was the average sea surface temperature during the summer, suggesting that the birds may be following changes in underlying marine resources. “The fact that individuals can be so flexible in the face of rapid climate change is encouraging.”
But despite this flexibility in their summer destination, Balearic shearwaters are much more limited in where they breed, so migrating further north means that They have more distance to fly back in the fall.
Co-author Professor Tim Guilford, also from the Department of Biology at the University of Oxford, added: “We found that individuals accelerate their return migration the further north they have gone, but this only partially compensates for the extra distance and they still return in the Mediterranean. late. “We don’t yet know how those 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 return to the colony. To investigate this, the researchers compared the distance estimates of the different types of maps that shearwaters could use to guide their migratory decisions.
Co-senior author Patrick Lewin (Department of Biology, University of Oxford) said: “We found that the route taken by individual birds on previous migratory journeys was a much better predictor of return speed than an estimate of straight-line distance. back to the colony. This suggests that the birds do not depend on a large-scale navigation map for migration, but they have a certain memory of the route they have followed in the past.
INDIVIDUAL ROUTE MEMORY
“It is possible that individual route memory plays a role an important role in the migration of many other long-lived seabirdsbut more research is needed to clarify this,” he added.
Balearic shearwaters belong to one of the most endangered groups of birds on the planet and face possible extinction as a species. This includes both terrestrial threats, such as predation by invasive species and habitat degradation, and threats at sea, such as fisheries bycatch, overfishing, pollution and wind farm development.
The results were published in the journal Proceedings of the National Academy of Sciences.
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