The researchers used birds equipped with geolocators to identify the routes they follow in their migratory travels. Cory’s shearwaters breed in Macaronesic and Mediterranean islands and winter offshore South Africa and Namibia. It was known that, rather than follow a straight route to cover the approximately 8,000 km that separate the Canary Islands from southern Africa, they follow a detour of 3,000 km, reaching Brazil. What is more, they fly using a very peculiar technique: surfing the air that ocean waves push in front of them. These two features made the Cory’s shearwater an ideal candidate for studying migration routes.

Given that waves are produced by wind, the data generated by the satellite QuikSCAT on wind characteristics were used to observe how shearwaters used the wind highways between Canary Islands and southern Africa. The authors found that birds follow very exactly the flyway route connecting these two points and that this can only be done during a very precise period of time as their southward journey can be closed because of calms or contrary winds. In 2004, a team of researchers had already demonstrated that invisible wind highways can explain why areas separated by thousands of kilometres can share a large number of species.

These results open new avenues of research, such as identifying when and where pathogens or invading species may spread in a specific area, when a treatment against these undesirable organisms can be more effective, or studying how species evolve after colonizing new areas.

For more information:
http://dx.plos.org/10.1371/journal.pone.0002928