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

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

© 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 © John M Baxter	Bass Rock © John M Baxter	Boreray, St Kilda © David Donnan/ SNH
Productivity and Abundance of breeding seabirds in Scotland (1986-2008) Source: UK Seabird Monitoring Programme		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

© Lorne Gill/ SNH

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

© Lorne Gill/ SNH

Atlantic puffin © Lorne Gill/ SNH	Seabird colonies in Scotland containing more than 1000 individual birds
Northern fulmar © John M Baxter
Common guillemot © Lorne Gill/ SNH	Common guillemots on Isle of Noss, Shetland © Lorne Gill/ SNH