The wide-ranging migration patterns of Sooty Terns, a tropical seabird, presents big challenges for conservationists working to understand and address a sharp population decline, according to scientists at the University of Birmingham and supported by academics from Hartpury University and the University of Exeter.
The new study, published in Frontiers in Marine Science, is one of the first to examine the potential conservation benefits of a Marine Protection Area (MPA).
The research, led by Dr Jim Reynolds who is based in the School of Biosciences at the University of Birmingham, and supported by fellow academics including Dr Sam Weber from the University of Exeter and Dr Lucy Garrett from Hartpury University, focused on the movements and behaviours of sooty terns. The birds are valuable bioindicators of the overall health of the marine ecosystem by virtue of their far-ranging migratory behaviour. Tern populations have declined from several million in the mid-20thcentury, to much-reduced population sizes that have remained relatively stable over the past 30 years.
The study focused on Ascension Island, designated a Marine Protection Area (MPA) in 2019. The MPA covers some 443,000 square km (170,000 square miles) with Ascension Island at its heart. The team used global location sensing (GLS) or ‘geolocator’ tracking data to show the migration patterns of sooty terns from the largest breeding population in the Atlantic. They found that birds ranged up to 2,900 km from their breeding colonies and covered some 47,000 km during an eight-month migratory period.
Geolocators were deployed on both male and female terns over a five-year period, from 2011-2015. In total, 90 tags were deployed, 30 of which were retrieved allowing downloading of positional data for analysis.
During the non-breeding season, researchers found the birds migrated over periods of about eight months, during which time they flew incredibly long distances. They spent most of the day and night in flight, probably sleeping ‘on the wing’ and only touching down on the ocean surface to feed.
Because the birds are travelling such as long distances on migration, the researchers predict that the benefits of the Marine Protection Area will be much more limited during the non-breeding season.
Dr Lucy Garrett, Lecturer in Animal Science at Hartpury University explained: “The findings of this study are significant in that they show the complex life stages of pelagic seabird species that migrate significant distances in order to find enough food during the non-breeding season.
“The designation of marine protected areas is paramount for the preservation and management of our vulnerable and diverse oceans and all they support. However, careful consideration as to the extent to which these MPAs can ‘solve’ or mitigate the effects of issues such as over-fishing needs to take place with a focus on the wider issues themselves.
“Although MPAs have been found to have positive effects on species numbers and conservation, there are often those which will rely on much larger areas, such as the sooty tern, and therefore an interconnected oceanic approach to the management of human uses of our oceans will be required.
Dr Garrett is currently seeking funding to continue her work with the sooty tern population to understand further the interconnectedness of the Ascension Island population with other breeding colonies in the South Atlantic Ocean. Such collaborative projects are vital to fully appreciate the movements and requirements of such ocean explorers.
Hartpury University is committed to research and knowledge exchange as a solution to real-world questions facing animals, agriculture and conservation. Learn more about Hartpury’s multi-disciplinary Animal and Agriculture Research Centre on our website.
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