RSPB surveys most threatened bird to visit Britain

Balearic Shearwater: In 1991 there were thought to be a total of 3,300 breeding pairs of Balearic Shearwaters, but since then it is estimated that the population has decreased by more than a third. Based on the dramatic decline in the decade since 1991, the species is considered to be critically endangered on a global basis. It is the only critically endangered bird regularly visiting the UK. (photo: Tom Brereton).

The RSPB is launching the first survey in UK waters to learn more about one of the most threatened seabirds in the world. The Balearic Shearwater – a miniature relative of the albatross – is the rarest bird in the world to visit Britain regularly.

It is believed there are fewer than 2,000 pairs of this critically-endangered seabird in the world, and experts on the species believe they could be visiting British waters in increasingly larger numbers – involving hundreds of birds – in late summer and early autumn, possibly as a result of climate change.

Balearic Shearwater: Balearic Shearwaters breed only on Mallorca, Minorca, Ibiza, Cabrera and Formentera in the western Mediterranean. The birds leave the Mediterranean for the Atlantic, notably Bay of Biscay, following breeding from June onwards, returning over the winter. (photo: Ben Lascelles).

Globally, this dove-sized bird only nests on five islands in the western Mediterranean, including the holiday hotspots of Majorca and Ibiza, where the bird faces threats from introduced cats and rats, and from increasing tourist development. Additionally, like the bird’s giant cousins – the albatrosses – Balearic Shearwaters regularly drown on longline fishing hooks, especially deep-water lines set for hake.

Carles Carboneras, a seabird expert with SEO - the RSPB’s partner in Spain – has studied Balearic shearwaters for many years. He said: “Many believe that because the Balearic Shearwater nests in the Mediterranean that it must love warmth. However, it prefers to leave the Mediterranean in mid summer and head north through the Bay of Biscay towards relatively cool British waters. It is a specialist of cold-water and the bird can no longer live where it used to.

“But with climate change warming the oceans, these seas will become less productive, and we believe these birds will probably need to move even further north to find sufficient food.”

Dr Mark Avery, the RSPB’s conservation director, said: “The Balearic Shearwater is one of the rarest birds in the world. Britain’s seas contain more animal species under threat of global extinction than our countryside does. The marine environment is the Cinderella of the conservation movement and the growing global importance of our waters is a call for urgent action by the Government and the European Union to protect our seas.”

RSPB conservation officer Helen Booker said: “These birds don’t come to land after breeding, and their fleeting contact with people makes them also one of the least-known birds in Britain. If we can observe them from land when they are here, we can hopefully determine what can be done to protect them.”

She added: “More than a hundred were recorded off Berry Head in South Devon in just one day this month – which is a significant proportion of the world population.”

Balearic Shearwater: Despite the fact there has previously been no systematic survey of the species, data shows that Balearic Shearwaters use the coast of the UK during the summer. RSPB calculations in 2001 determined that the average UK population was 1543 birds per year between 1995 and 1999. The majority of these birds were recorded off the coasts of Devon, Cornwall and Dorset between the months of July and October. (photo: Gary Thoburn).

The pilot study of the birds, involving synchronised counts at different locations, will add to information gathered by land-based birdwatchers and will hopefully provide a fuller picture of the life of the Balearic Shearwater.

Dr Russell Wynn of National Oceanography Centre, Southampton is also studying the birds. He said: “Balearic Shearwaters are venturing north to our coastal waters in increasing numbers, even though the species is declining and may become extinct within our lifetime. I’m collaborating with oceanographers and biologists at NOC to understand why they are moving north, and am working with the RSPB to expand the pilot survey next year.”