The paper clip-sized tracker exhibits the intrepid journey of Britain's smallest seabird

Why weren't researchers able to track the European petrel until recently?

European petrels, Hydrobates pelagicus, are extremely small – the size of a sparrow and the second smallest seabird in the world. High-precision GPS tags for such a tiny species have only become available in the past few years. The trackers we use weigh less than a gram and can record the location of the bird anywhere in the world with an accuracy of a few meters. Over a period of four years we have tracked 42 petrels on Mousa Island in the Shetland Islands in the UK.

What were your most important insights?

We found that petrels, while having a large foraging range and regularly more than 200 kilometers from the colony, consistently use a relatively small marine area, much of which has already been designated a marine reserve due to its importance to other species. With our new data, we found that the petrels' daily forage area and the waters immediately adjacent to the colony where the birds were commuting both met what should be considered important marine bird and biodiversity areas (IBAs). Since petrels only visit their colony when it is dark, their “commuter areas” would not have been recognized with conventional visual surveying methods.

Were there any surprises?

One of the birds we were chasing was caught in a strong storm and blown across the North Sea to Norway to take shelter in a fjord north of Stavanger. When I caught it upon its return, I found that it had gained weight during its trip and that its chick had been fed. So not only had the bird survived being driven to Norway by the storm, but it had also managed to find food for itself and its nest along the way. It is likely that all of the birds that feed on that day had the same conditions. In fact, petrels are so named because they are usually only spotted near land in high winds.

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How can this study help protect the European petrel and other sea birds?

The birds we have tagged are part of the largest colony of petrels in the UK, an internationally important sanctuary. In principle, all petrels that breed in this colony are therefore protected when they are feeding at sea. However, if we do not know exactly where they feed, it is very difficult to assess the possible effects of marine activities and put this protection in place. This study provides the information we need to do this. In addition, the areas that qualify for IBA marine status can now be recommended for legal protection. Both areas coincide with marine protected areas that have been designated for different reasons and underscore the importance of certain areas for a whole range of marine biodiversity.

GPS tracking shows that European petrels, Hydrobates pelagicus, are very consistently restricted to foraging for food in the UK's largest colony: the effects on conservation management are published in Bird Conservation International.

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