As part of a national drive to count the UK's breeding seabirds, this summer a hardy band of fieldworkers will be searching two Pembrokeshire islands, Skokholm and Skomer, for the most mysterious seabird in Wales - the European Storm petrel.
These islands form the Skokholm and Skomer Special Protection Area (SPA) and are world famous for their seabirds, with internationally important numbers of breeding Atlantic puffins and common guillemots delighting visitors by day, and half the world's population of Manx shearwaters coming out of their burrows by night. But as night falls, the Atlantic's tiniest seabird comes ashore to the breeding colonies among the rocks, boulders and scree slopes of these wild Welsh islands.
Storm petrels are related to the world's most famous ocean wanderers, the albatrosses, but weigh only about as much as a sparrow. Despite their diminutive size they range far out at sea for most of the year, braving the wildest of weather and spending our winter off the coasts of South Africa.
Perhaps 5,000 European Storm petrels breed on Skokholm Island, representing up to 20% of Europe's breeding population, and a few hundred on Skomer, but no one really knows simply because they're notoriously difficult to count. If you turn on a torch they fly away, if you disturb them in their breeding burrows they tend to desert their nest. And they nest in inaccessible places, so it's understandable that ornithologists have to think smart to count storm petrels without disturbing them. Which is why Skokholm volunteer Vicky Taylor will be listening to fairies being sick for the next few weeks!
"We play the sound of a singing storm petrel to a likely nest site," says Vicky, "and if there's a bird in there it often calls back. It's supposed to sound like a fairy being sick, but I think it's more like a purring cat with the hiccups!" The distinctive smell of storm petrels can also reveal a nest. "It's a musty, oily smell, but distinctly pleasant," says Skomer Assistant Warden Jason Moss. "If you get a strong whiff it can help to locate a nest burrow or a new breeding colony."
The survey technique has been refined over the years, but 2016 sees the first attempt a complete census of the largest European Storm petrel breeding colony in England and Wales: the 'Quarry' on Skokholm Island. Warden Richard Brown says, "The Quarry is a natural amphitheatre of old red sandstone where hundreds of storm petrels nest in fragile crevices. Work there is challenging and requires careful planning, but what an office!"
The survey is a great example of cooperation between conservationists, seabird biologists, and government agency: the project is carried out by the Wildlife Trust of South & West Wales & the University of Gloucestershire, with funding and support from Natural Resources Wales.
Mike Evans, Head of Evidence, Knowledge and Advice at Natural Resources Wales added: “As an evidence-based organisation, it is critically important for us to have a good understanding of our changing environment. We know that we have a very healthy marine environment here in Wales, and by having a better understanding of the wildlife that thrives here, will allow us to give the very best advice we give to government, European Commission and to others.”
Dr Matt Wood from the University of Gloucestershire is coordinating the survey: "We need good counts of our seabirds to be able to see how they get on year by year, to monitor the UK's amazing seabird populations. Seabirds are excellent sentinels for the health of our oceans, I'm really looking forward to seeing how many storm petrels we have here so we can safeguard the population for future generations."
Photograph courtesy of Dave Boyle.