Blog by Dr Mark Bolton, Principal Conservation Scientist on his new paper published today. 

The sparrow-sized European storm petrel is the smallest seabird in the Atlantic, nesting only on the most remote islands, around the coasts of north-west Europe. Over the last century, seabird biologists working in these far flung and beautiful places have pieced together the details of the storm petrels’ breeding behaviour on land. We know that they only visit the nesting colony under the cover of darkness, and parents take turns to incubate their single egg for periods of up to three or four days, without feeding, whilst their partners remain at sea.

However, until now, our understanding of their activities at sea was based largely on guesswork. We knew from boat surveys that the highest densities occurred along the edge of the continental shelf, bordering the open ocean. We knew little about the comings and goings of these tiny birds between the foraging areas and the nesting islands.

Storm petrel at sea (c) Mark Bolton

The recent development of miniature GPS tracking tags has provided researchers with a remarkable new tool that enables us to accompany these tiny birds on their foraging trips. It allows us to understand for the first time, their movements, behaviour and distribution at sea.  The information we can now obtain provides fascinating insights into the birds’ daily lives. This will produce vital evidence to ensure that important areas for feeding and commuting are well-managed, and ensure the continued survival of these remarkable seabirds.

The study site and tracking work

The work was carried out on the RSPB reserve of Mousa in the Shetland Islands, which is home to around 11,000 pairs of storm petrels, the largest breeding colony in UK, and around 2% of the global population. The birds nest in crevices in dry stone walls, boulder beaches and ruined buildings. Storm petrels have been studied on Mousa for nearly 30 years, and the nesting areas and individual pairs are well-known, enabling the birds to be carefully handled to attach and remove tags with the minimum of disturbance. Over the course of four years birds were tracked during different stages of the breeding cycle – when they had eggs, small chicks, and later in the season when the chicks were larger.