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Scotland's Marine Atlas: Information for The National Marine Plan

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SEABIRDS

Scotland holds internationally important numbers of 24 species of breeding seabirds that are an important indicator for assessing the state of the marine environment. Seabirds respond to a range of factors, such as changes in food availability, weather, predation and pollution. Their abundance (i.e. number of breeding birds) is determined by how many adults survive from the previous year and how many young birds successfully reach maturity. The productivity (i.e. number of chicks produced) can provide a good indication of food availability as well as levels of predation. Productivity typically changes more quickly than abundance.

Breeding abundance and productivity is assessed for a number of the species that breed in Scotland based on a representative sample of colonies around Scotland, which are monitored as part of the UK Seabird Monitoring Programme. Seabird abundance has been declining since the early 1990s, the lowest abundance (70% of 1986 level) was reached in 2004 and has subsequently increased slightly and has been stable at around 72% for the last three years. The abundance declines were driven by those of black-legged kittiwake, Arctic skua, Arctic tern, herring gull, European shag, great black-backed gull and Sandwich tern and latterly by those of northern fulmar and common guillemot. Seabird productivity has fluctuated over the period but has declined to a low of 57% in 2007, since when there has been a very slight increase.

Black-legged kittiwake

Black-legged kittiwake
© Lorne Gill/ SNH

Breeding seabird numbers

Species

Scotland

UK Total population

Scotland as percentage of UK population

Northern fulmar Fulmarus glacialis

485,852

501,609

96.8

Manx shearwater Puffinus puffinus

126,545

299,678

42.2

European storm-petrel Hydrobates pelagicus

21,370

25,650

83.3

Leach's storm-petrel Oceanodroma leucorhoa

48,047

48,047

100

Northern gannet 1Morus bassanus

182,511

218,546

83.5

Great cormorant Phalacrocorax carbo

3,626

8,884

coastal component 2

3,626

7,238

50.1

European shag Phalacrocorax aristotelis

21,487

26,565

80.9

Arctic skua Stercorarius parasiticus

2,136

2,136

100

Great skua Catharacta skua

9,634

9,634

100

Black-headed gull Larus ridibundus

43,191

138,012

coastal component 2

6,888

77,324

8.9

Mew gull Larus canus

48,113

48,714

coastal component 2

20,467

20,883

98.0

Lesser black-backed gull Larus fuscus

25,057

111,960

coastal component 2

21,565

87,413

24.7

Herring gull Larus argentatus

72,130

132,183

coastal component 2

71,659

130,228

55.0

Great black-backed gull Larus marinus

14,776

16,755

coastal component 2

14,773

16,735

88.3

Black-legged kittiwake Rissa tridactyla

282,213

378,847

74.5

Sandwich tern Sterna sandvicensis

1,068

12,490

8.6

Roseate tern 3Sterna dougallii

5

107

4.7

Common tern Sterna hirundo

4,784

11,838

40.4

Arctic tern Sterna paradisaea

47,306

53,380

88.6

Little tern Sterna albifrons

331

1,927

17.2

Common guillemot 4Uria aalge

1,167,841

1,416,334

82.5

Razorbill 4Alca torda

139,186

187,052

74.4

Black guillemot 5Cepphus grille

37,505

38,714

96.9

Atlantic puffin Fratercula arctica

493,042

580,714

84.9

Breeding seabird numbers in the United Kingdom. Most figures are from the Seabird 2000 survey (1998-2002) but those for Northern gannet and roseate tern include more recent updates. All counts are of pairs unless otherwise stated.
1 Northern gannet figures are from the complete UK and Ireland survey of colonies in 2003-2005.
2 For species which also breed in inland colonies (defined as those >5km from the sea) the coastal component is shown separately.
3 Roseate tern figures are from 2006.
4 Counts are of individuals.
5 Counts of pre-breeding adults.

Abundance and Productivity Indicators

Species

Abundance index

Productivity index

1986

2009

1986

2009

Arctic skua

100

47.73

1

0.68

Arctic tern

100

94.08

1

2.43

Atlantic puffin

1

0.95

Black guillemot

100

62.87

Common tern

100

98.67

1

0.33

Northern fulmar

100

80.47

1

0.79

Great black-backed gull

100

53.62

Great skua

100

330.02

1

1.11

Common guillemot

100

82.00

1

0.80

Herring gull

100

45.18

1

1.17

Black-legged kittiwake

100

42.79

1

0.84

Lesser black-backed gull

1

1.33

Little tern

1

1.14

Sandwich tern

100

56.83

1

0.0004

European shag

100

57.82

Northern gannet

Northern gannet
© John M Baxter

Bass Rock

Bass Rock
© John M Baxter

Boreray, St Kilda

Boreray, St Kilda
© David Donnan/ SNH

Productivity and Abundance of breeding
seabirds in Scotland (1986-2008)

Productivity and Abundance of breeding seabirds in Scotland (1986-2008)
Source: UK Seabird Monitoring Programme

Northern fulmar

Northern fulmar
© John M Baxter

Major Seabird Colonies in Scotland

Colony name

Species

Count at last census
(Seabird 2000: 1998-2002)

1. Boreray, St Kilda

Atlantic puffin

51,000

northern fulmar

5,000

northern gannet

61,000

Leach's petrel

13,000

2. Rum

Manx shearwater

120,000

black guillemot

645

3. Dun, St Kilda

Atlantic puffin

55,000

northern fulmar

11,000

Leach's petrel

28,000

4. Fair Isle

Atlantic puffin

40,000

northern fulmar

20,000

European shag

700

great skua

140

Arctic tern

1,300

common guillemot

39,000

5. Forth Islands - Bass Rock to Haystack
(excluding Isle of May)

Atlantic puffin

30,000

herring gull

6,000

lesser black-backed gull

5,000

northern gannet

44,000

6. Shiant Islands

razorbill

8,000

Atlantic puffin

65,000

great black-backed gull

300

European shag

500

common guillemot

16,000

7. Caithness south-eastern Cliffs

razorbill

7,000

northern fulmar

7,000

herring gull

1,400

European shag

800

black-legged kittiwake

24,000

common guillemot

79,000

8. Handa Island

razorbill

17,000

Arctic skua

42

great skua

195

common guillemot

113,000

9. Foula

Atlantic puffin

23,000

northern fulmar

21,000

European shag

2,000

great skua

2,000

Arctic skua

110

common guillemot

41,000

10. Caithness north-eastern Cliffs

razorbill

11,000

northern fulmar

8,000

herring gull

2,000

black-legged kittiwake

16,000

common guillemot

80,000

Note: Colonies ranked on total number of individual breeding seabirds at last census in 1998-2002. A selection of the most notable species is given. Some colonies have been re-counted since last census, but these are not shown. All figures are pairs, except for razorbill, common guillemot and black guillemot, for which individuals are given.

Priority Marine Feature

Black guillemot - Cepphus grylle

Black guillemots (known as tystie in Shetland) are widely distributed around the Scottish coast, but with the main concentrations in the Northern Isles and west coast. The Scottish population of ~38,000 represents about 87% of the Britain and Ireland population and of these over 50% breed in Shetland and Orkney.

Pressures

Black guillemots are very vulnerable to oil spills and predation at their nests by otters and American mink. Some local declines have been linked to mink predation.

Black guillemot - Cepphus grylle

Black guillemot - Cepphus grylle
© Lorne Gill/ SNH

Black guillemot - Cepphus grylle map

Pressures

The key factors affecting the abundance and productivity of seabirds are food availability, weather conditions and the occurrence of predators. Many seabirds, particularly those that have undergone the largest declines, mostly feed on small shoaling fish such as sandeels. In the past commercial sandeel fishing has had a detrimental impact on black-legged kittiwake survival and productivity. There is little sandeel fishing off Scotland currently due to fishery closure and stock collapse. Sandeel abundance appeared to be high again in 2009 and this is reflected in improved productivity in a number of species. Changes lower down the food chain caused by warming sea water temperatures are also thought to have contributed to the reduction in sandeel abundance, size and energy content, especially in the North Sea. Fisheries have also contributed to earlier increases in some seabirds that scavenge offal and discards, such as the northern fulmar and great skua. Great skuas have continued to increase in numbers but northern fulmars have declined in recent years. Predation by non-native mammals has caused reductions in productivity and abundance of ground and burrow nesting seabirds. Successful eradication of these predators at a local scale has started to have benefits for seabirds in recent years.

The traditional guga hunt on Sula Sgeir to the north of Lewis in the Outer Hebrides is licensed to take up to 2000 young northern gannet chicks that are eaten as a local delicacy.

Razorbill

Razorbill
© Lorne Gill/ SNH

Atlantic puffin

Atlantic puffin
© Lorne Gill/ SNH

Seabird colonies in Scotland containing more than 1000 individual birds

Seabird colonies in Scotland containing more than 1000 individual birds

Northern fulmar

Northern fulmar
© John M Baxter

Common guillemot

Common guillemot
© Lorne Gill/ SNH

Common guillemots on Isle of Noss, Shetland

Common guillemots on Isle of Noss, Shetland
© Lorne Gill/ SNH