Mystery of bird movements at sea solved

Unprecedented use of innovative GPS tracking and computer models to map where British and Irish breeding seabirds go to feed has revealed unique insights into their distribution.

New research published in conservation journal Ecological Applications used five years of seabird GPS-tracking data and powerful computer modelling methods to estimate the areas of sea used by four of Britain and Ireland’s breeding seabird species. For the first time on a national scale, this has enabled scientists to predict where birds go foraging at sea.

This comes as British administrations are considering creating protected sites at sea to safeguard key seabird feeding areas, as well as planning future fisheries policy for UK territorial seas once outside the EU's Common Fisheries Policy post-Brexit. These new findings will provide critical information for the future management of the marine environment.

The RSPB's Ellie Owen releases an adult male Shag, recently fitted with a GPS tag (RSPB).

The study maps the extensive areas of sea that Kittiwake, Shag, Razorbill and Common Guillemot use and has shown the extent to which birds will travel from their nests in search of food, proving just how crucial our seas are for seabirds and their young. This is a major step forward in our understanding of seabirds and a powerful tool to help protect them from potentially harmful activities at sea.

During the five-year project, lightweight GPS tags were fitted to more than 1,300 adult birds from 29 different colonies. The tracking data was then used to create a computer model for each species so that important sea areas for untracked colonies could also be predicted. The results show that the four species use at least 950,000 square miles of sea, an area three times the size of Spain.

Dr Mark Bolton, RSPB principal conservation scientist, said: “This new research is further evidence of just how important our seas are for seabirds and their chicks during the breeding season. In order to strengthen this research and our predictions, there is an urgent need for a complete seabird census which will provide an accurate and up-to-date estimate of the size of our seabird breeding colonies.”

Seabirds are among the most endangered groups of birds in the world, partly due to the impacts of climate change and fishing. Of the four species studied, red-listed Kittiwake and Shag numbers have declined by 71 per cent and 62 per cent respectively in the last 25 years. Razorbills and Common Guillemots are amber listed, and also require conservation action.

GPS tagging has shown that Kittiwakes forage far from their nesting colonies (RSPB).

A recent OSPAR report highlights widespread seabird breeding failures occurring frequently in the six-year monitoring period for 35 per cent of species assessed in the greater North Sea and 25 per cent in the Celtic Seas.

Dr Ewan Wakefield, lead author of the research, commented: “Many seabirds are at the top of the marine food web. They feed on sand-eels and other small fish, but that prey is declining because of human pressures, including climate change. The result is that thousands of seabird chicks are dying each year because their parents can’t feed them.

“Thanks to the results from this research and the methods used, scientists will be able to provide better evidence for those important areas of sea that should be part of protected areas and help to improve how we plan for development at sea to reduce conflicts between the needs of our seabirds and human activities.”

Ellie Owen holding an adult male Shag recently fitted with a GPS tag (RSPB).