An SNH report on the decline in Scottish Seabird numbers

Decline in Scotland’s seabird numbers 

A new report by Scottish Natural Heritage (SNH) reveals that Scotland’s
seabird numbers fell by 19% 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 Government’s Marine Bill, launched this spring,
includes measures to improve marine nature conservation to safeguard and protect
Scotland’s unique marine species and habitats.

Professor Colin Galbraith, SNH Director of Policy and Advice, said:  “While
it’s always disappointing to witness declines in important species, we are not
entirely surprised at these findings. That’s 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. We need to
keep a close eye on seabird trends and try to understand what is driving them.
What is clear is that the overall decline has not worsened over the past
year.”

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% fewer black-legged kittiwake
and 71% fewer Arctic skuas breeding in Scotland than in the mid 1980s. Arctic
terns declined by 26% 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% 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.

Deryk Shaw, Warden of the Fair Isle Bird Observatory in Shetland, said: 
“Breeding kittiwake numbers have been falling for many years now and there
was no reprieve in 2008. A whole island count for the Fair Isle found that the
number of nests is only half of that counted as recently as 2005 with many birds
just standing on bare ledges.” 

In comparison, 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.

On the island of Canna, rats were eradicated in 2005/6. Richard Luxmoore, of
National Trust for Scotland, which manages the island, said: “Since we removed
the rats, numbers of species such as European shags and Atlantic puffins have
started to increase after several years of decline, though there is a long way
to go to full recovery.” 

A concurrent report by the Joint Nature Conservation Committee (JNCC), the UK
Government’s advisor on nature conservation, revealed a UK-wide decline of 9%
since 2000.

Dr. Matt Parsons from JNCC, one of the JNCC report’s 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.” 

 The Scottish Seabird Indicator is part of a suite of biodiversity indicators
(http://www.snh.org.uk/trends/trends_notes/pdf/B377378.pdfSF) which are used to
assess the state of Scotland’s biodiversity.