Decline in Scotlands seabird numbers Published: 11 June, 2009
A new report by Scottish Natural Heritage (SNH) reveals that Scotlands seabird numbers fell by 19 per cent between 2000 and 2008.
The major cause of these declines is almost certainly a shortage of food due to a drop in the number of small fish, such as sandeels. These fish are likely being affected by rising sea temperatures because of climate change.
Lower fish numbers lead to lower numbers of adult birds surviving from one year to the next, and not enough chicks being produced and surviving to replace them. A range of measures has already been put in place to help address pressures on the seabirds. Voluntary reduction in sandeel fisheries means that very little if any sandeel fishing now takes place within foraging ranges of seabirds especially kittiwakes, a species which saw a particularly sharp drop in numbers.
Intensive trapping of predators, such as the brown rat and the non-native American mink, is also being carried out in various parts of the Scottish coastline and islands. This is to reduce the extent to which these species take seabird eggs and chicks.
Importantly, the Scottish governments Marine Bill, launched this spring, includes measures to improve marine nature conservation to safeguard and protect Scotlands unique marine species and habitats.
Professor Colin Galbraith, SNH director of policy and advice, said: ‘While its always disappointing to witness declines in important species, we are not entirely surprised at these findings. Thats why various measures are already in place to improve the situation for seabirds. After several decades of increasing seabird abundance, we are now witnessing a period of decline. Key reasons are likely to be linked to food availability, weather, and predation. In particular, climate change appears to have affected plankton abundance at the
base of the food web.’
He added: ‘It is important that we are now able to monitor seabird numbers much more effectively than in the past, to inform policy and action.’ Scotland is home to around four million breeding seabirds of 24 species. The recent drop in numbers follows two decades of occasional years of poor breeding – but poor years have happened more often and with more severity since 2000.
Recent declines are greater in species that feed on shoals of small fish, such as lesser sandeels: for instance, there are now 55 per cent fewer black-legged kittiwake and 71 per cent fewer Arctic skuas breeding in Scotland than in the mid 1980s. Arctic terns declined by 26 per cent over the same period.
There are some winners, however. Great skuas, which have a varied diet – from other seabirds to scavenging fishery waste at sea – have increased dramatically since the mid 1980s, and razorbills increased by 47 per cent over the same period. Declines have been greater in areas such as the Northern Isles and down the east coast. This is largely because sandeels have declined and there are fewer alternative prey.
Seabirds along the west coast of Scotland and further south in
the Irish Sea rely less on sandeels and take more sprat and herring. These areas have not suffered the same declines of sandeels as seen in the North Sea.
A concurrent report by the Joint Nature Conservation Committee (JNCC), the UK Governments advisor on nature conservation, revealed a UK-wide decline of 9% since 2000.
Dr Matt Parsons from JNCC, one of the JNCC reports authors, said: ‘These latest figures on breeding numbers demonstrate what a massive effect these poor seasons have had on the UK seabird population. They represent a turning of the tide for seabirds breeding in Scotland, which increased in number from the late 1960s to the end of the 1990s.’