UK seabirds under pressure

 

UK seabirds have suffered a 9% drop in numbers since 2000, reveals UK Seabirds in 2008,* a report from the UK Seabird Monitoring Programme.

 

The recent decline (amounting to over 600,000 birds) follows years of poor breeding performance that have occurred with greater frequency since the mid-1990s. “These latest figures on breeding numbers demonstrate the magnitude of the effect these poor seasons have had on the UK seabird population,” said Matt Parsons, Seabird Monitoring Programme Co-ordinator. “They represent a ‘turning of the tide’ for seabirds breeding in the UK, which increased in numbers from around 4.5 million in the late 1960s to 7 million by the end of the 1990s.”

 

Species that have been particularly badly hit are those that feed on shoals of small fish such as lesser sandeels. For instance, there are now 40% fewer black-legged kittiwake and 33% fewer European shags breeding in the UK than in the late 1960s. The cause of these declines is almost certainly a shortage of food that has led to lower numbers of adults surviving from one year to the next, and not enough chicks being produced and surviving to replace them.

 

The reasons for the shortages of sandeels in recent years are complex and not fully understood. Over-fishing off eastern Scotland had a significant detrimental effect on the productivity of kittiwakes at nearby colonies during the 1990s, but little fishing has occurred within foraging range of these colonies since then. Fishing may be affecting the distribution and abundance of sandeels across the entire North Sea, but it is not clear whether this has influenced the availability of sandeels to seabirds feeding closer inshore. There is a growing body of evidence that sandeel shortages are also caused by increasing sea temperatures as a result of climate change. Sea temperatures around the UK have been rising since the 1980s by around 0.2–0.9˚C per decade. These rises are thought to have been responsible for striking changes in the abundance of plankton – the tiny floating organisms that sandeels and other small fish feed on.

 

Long-term declines in numbers of black-legged kittiwakes and other species that rely on sandeels are expected to continue unless the rises in sea-surface temperature are reversed. Reversing the recent warming of the oceans is reliant on the success of global efforts to combat climate change. However, the report identifies two other man-made pressures – from fishing and from the introduction of non-native mammals to island seabird colonies – that could be managed in the short-term to mitigate the impacts of climate change.

 

Matt Parsons

SMP Co-ordinator

Tel: +44 (0) 1224 655715