Birds are one of the best indicators of the health of the planet: they are alerting us to climate change, global warming and its consequences. This is demonstrated once again by a new study published this week in the journal Proceedings of the National Academy of Sciences (PNAS), which explores the movements of what is considered the most endangered seabird in Europe: the Balearic shearwater. The main conclusion of the research is that this species shows a tendency to move increasingly north in search of feeding places in the Atlantic.
The reason is climate change. As sea temperatures increase, the Balearic shearwater is forced to move following the movements of its prey. Otherwise, they would be left without food.
The study, led by researchers from the University of Oxford and the result of a collaboration between several British, Spanish and French entities, including SEO/BirdLife, is based on the analysis of almost a decade of monitoring (2010-2018). . During this period, Balearic plot specimens ('Puffinus mauretanicus') were marked annually in four colonies in the Balearic Islands, two of them in Ibiza (Sa Conillera and Es Bosc) and another two in Mallorca (Sa Cella and Dragonera).
The researchers studied their movements throughout the entire annual cycle. To do this, they used geolocators, small devices that measure and record light levels and allow their position to be inferred over time. In more detail, knowing the length of the day you can estimate the latitude at which the birds are located and knowing the time of sunrise and sunset you can determine the longitude.
When shearwaters go out to the Atlantic at the beginning of summer, after breeding in the Balearic Islands, they concentrate in two main areas: the northwest of the Iberian Peninsula and French Brittany.
The data suggests that more and more shearwaters are visiting Brittany, while a movement towards the north is observed in the most frequented areas within each of these areas.
“Maintaining long-term monitoring programs is essential to understand the evolution of bird populations and the response to changes that occur in their environment,” says Pep Arcos, coordinator of the SEO/BirdLife marine program and one of the co-authors. from the article.
Arcos adds: “In addition, it is not only about understanding what happens with birds, but they are excellent indicators of the state of conservation of the marine environment.”
On the other hand, the study indicates that Balearic shearwaters are flexible enough to adapt individually to changes and would be able to learn migratory routes and adapt their return flights thanks to the accumulated knowledge.
Although shearwaters can fly hundreds of kilometers from the nest to find food, their natural prey - mainly small pelagic fish such as sardines and anchovies - are becoming increasingly scarce in the Mediterranean. Accessing areas rich in food may require much longer flights than usual, which could very negatively affect their reproduction.
“They only breed in the Balearic Islands, and their philopatry makes it difficult to think that they are capable of moving to other areas to breed in the future. Thus, the species, classified as 'critically endangered' at a global level, adds a new obstacle to other threats already documented, such as accidental capture in fishing gear, predation by species introduced in its colonies or different forms of pollution," Arcos emphasizes.
In this regard, Arcos concludes: “Ironically, another new threat to the species is offshore wind development, which is precisely presented as the spearhead in the fight against climate change.”
