Pete Bevington

10 August, 2009

ORNITHOLOGISTS in Shetland have been heartened by the best seabird breeding season for years, but they still have no explanation for the change.

An apparent abundance of sandeels, the staple diet of many seabirds, seems to have given rapidly depleting species like kittiwakes, guillemots and arctic terns some respite from the downward trend of the past decade.

The past two years have been particularly poor. Last year on the RSPB bird reserve on Mousa 400 pairs of arctic terns failed to fledge a single chick. This year 1,000 pairs on the same island have raised 500 chicks successfully.

Scientists are refusing to call it a recovery, and admit they have no idea why there is more food available this year.

Martin Heubeck, of Aberdeen University, who has monitored Shetland’s seabirds for the past three decades, said this is the best it hass been since 2000.

“By and large it looks like a reasonable season. It’s not going to bring everything back to what it used to be, but it will slow or halt the slide. We have to take it one year at a time,” he said.

Overall the seabirds on Shetland are far less numerous than they used to be and their general condition has deteriorated. In 1998 there were 55,000 pairs of kittiwakes, a figure that has since fallen to just 10,000, partly due to predation.

Mr Heubeck said the marine environment was changing at such a rapid rate that seabirds were finding it hard to adapt, and scientists are finding it difficult to stay on top of what is going on.

“Even in such a small geographic region as Shetland it’s hard to keep up. It’s become much less uniform than it used to be. Where in the past you could say in general seabirds had a bad or very good year, now there’s more exceptions.

“Last year shags had their best breeding season in 21 years at Sumburgh Head, but hardly bred on Fair Isle.

“It’s obviously to do with the influence of the climate and oceanography and that’s affecting the entire food chain from phytoplankton up to the top predators. These things are changing faster than people can crunch the numbers.”

RSPB warden Helen Moncrieff said the puffins had a good year at Sumburgh, but had been behaving strangely. Last week they all left the cliffs early, a sign that they were well fed and ready to go. However a few days later they all came back again and since then they have been coming and going.

“It’s heartening to see a better season and it would be great if we had a run of better breeding seasons,” she said.

“I try to be an environmental optimist but I have learned that even if things look promising it can all change.”