New research has just been released which maps out the most important areas for Britain and Ireland's seabirds when they go out to sea to feed, with the majority of the 'hotspots' being found off the coast of Scotland. Rich Howells, from the marine team at RSPB Scotland, brings us this latest blog explaining a bit more about the research and what it means for seabird conservation.
Photo credit: Gary Howells.
A razorbill launches out to sea, but where is it going?
There are many things we know about Scotland’s seabirds: we know a guillemot found on Canna in 2016 was 38 years old, making it the UK’s oldest known seabird; we know gannets breeding on Bass Rock can travel a huge 540km in a single foraging trip to find food; and we know shags at Sumburgh Head dive to an impressive 61m in pursuit of their prey. We also know from long term studies that many seabird populations are declining, in some instances rapidly, due to a combination of factors including climate change, over-fishing and introduced predators.
Surveys from aeroplanes and boats have given us a good idea of where seabirds go at sea when they travel from the breeding colony to find food. Indeed this knowledge has allowed the identification of areas that qualify as Special Protected Areas (SPAs) under the EU Birds Directive. However, a gap free picture, allowing us to assess exactly where birds go and just how important areas of sea are for seabirds would need us to track individual birds from every single colony in Britain and Ireland, not an easy task with over 3,000 colonies hosting somewhere in the region of eight million birds of 25 different seabird species. But is there another way?
Sandeel is the main prey of many seabirds in Scotland. Photo credit: Steve Garvie.
In a landmark study and using a small team of expert bird catchers, RSPB scientists, working with researchers from institutes and organisations across Britain and Ireland, combined GPS tracking and mathematical modelling to identify the foraging areas that are most used by Britain and Ireland’s breeding seabirds, and found that the majority are concentrated around the coasts of Scotland.
Seabirds are among the fastest declining group of birds globally. Although our shores host internationally significant populations, breeding seabird numbers have fallen by 22% across the UK over the last 30 years. Declines are most severe in Scotland where breeding numbers in 2015 were 50% down on the 1986 level, when reporting began. This new research has important implications for the protection of seabirds, as without this kind of knowledge it is extremely difficult to reliably assess the impacts of developments, fisheries or other human activities on their breeding colonies.
Although much scientific attention has been paid to seabirds during breeding (for example see here), this has been predominantly focused on the nest, where birds are relatively easy to monitor. Until recently, studying seabirds away from their breeding sites involved observing birds from boats and planes. This provided a snapshot of where seabirds fed, but it was usually impossible to identify which colonies these birds had come from.
Traditionally, seabird studies were restricted to monitoring birds at their nests, or from boats and planes at sea. Photo credit: Gary Howells.
Recent advances in tracking technologies have miniaturised data-loggers to the point that they can be safely attached to the backs or tails of seabirds, allowing us to follow their foraging movements while out on the open ocean. By studying more than 1,300 adult birds from 29 different colonies, scientists were able to use this approach to track the foraging movements of four seabird species: shags, kittiwakes, guillemots and razorbills.
A kittiwake wearing a GPS tag on its back.
The inaccessibility of many seabird colonies further limits our understanding of seabird populations at a national level, and even where colonies are accessible, not all can be monitored. Remarkably, using what the tracking revealed about where birds go, the authors were able to model the foraging distributions of seabirds at colonies where individuals had not been tracked; a gap free picture emerges, predicting where these species go from more than 5,500 breeding sites around Britain and Ireland.
Predicted use of marine environment by four UK seabirds.
This new information allows us to assess the potential impacts of activities around our shores on seabirds, such as offshore renewable developments and different types of fisheries. It could also help in identifying colonies most at risk from specific threats like oil spills. Crucially, by identifying the areas used most intensively by foraging seabirds, conservationists and policy makers can more accurately identify sensitive areas for seabirds which will be relevant for the designation of Marine Protected Areas and marine spatial planning.