Sites of Special Scientific Interest (SSSI)
The 36 Sites of Special Scientific Interest (SSSI) in the Orkney Islands are located at:
A small low-lying island, Auskerry lies to the north-east of the Orkney mainland and 5 km south of Stronsay. It covers an area of approximately 1.5km by 1 km and is an internationally important breeding ground for Storm petrel and Arctic tern. Storm petrels nest mainly in old rabbit burrows and Arctic terns nest in groups, tending to use different areas of the island from year to year. The rare Iceland yellowcress grows here, along with the nationally scarce fern, small adderstongue.
The rocks of Bay of Skaill represent sediments of the Old Red Sandstone which were deposited in the Devonian geological time period, about 380 million years ago. They are composed of the Upper and Lower Caithness Flagstone with the intervening Sandwick Fish Bed. This middle Devonian fish bed is also characterised by containing a distinct floral assemblage. The Bay of Skaill fish bed contains fossils of Protopteridium thomsonii, the earliest known progymnosperm, plants which are the ancestors of present day conifers. It is also the only known British site to yield Barnandeina, a fossil genus also found in Bohemia.
The Calf of Eday is a small island off the north-east coast of Eday. It supports around 30,000 breeding birds of 12 different species, including 200-300 pairs of cormorant. Britain’s largest colony of great black-backed gull nest on the island, along with guillemot, Arctic skua, great skua, fulmar, Arctic tern, shag, herring gull, kittiwake, razorbill and black guillemot. The land is covered by heather, with smaller areas of wet heath, semi-improved grassland and coastal grassland.
The biggest and most complex sand dune system in Orkney is to be found in this area of Sanday. The coastal landscape contains a mix of blown sand and shingle landforms including tombolos (natural causeways linking headlands and islands), spits, bars, sand flats, dunes and machair. The site contains important plant habitats, including salt marsh, dunes and machair. Flowers abound on the salt marsh with the largest numbers of sea aster and annual sea-blite to be found in Orkney. Birdsfoot trefoil, lady’s bedstraw and heart-ease pansy flower amongst the marram grass on the dunes. Machair is one of the rarest habitats in Europe and the two areas on the site are species rich. Flowers to be found include lesser meadow rue, thyme, limestone bedstraw, fairy flax and felwort. Growing on wetter areas are jointed rush, grass of Parnassus, lesser clubmoss, curved sedge and lesser marsh orchid.
Copinsay and the three smaller islets of Corn Holm, Ward Holm and Black Holm lie 4 km off the east coast of Deerness. Copinsay is backed by approximately 1.5km of steep cliffs, which rise to more than 60 metres in height. These support a large colony of breeding seabirds including guillemot, kittiwake, great black-backed gull, fulmar, shag, lesser black-backed gull, herring gull, common gull, razorbill, black guillemot and puffin.
The qualifying interests in this site lie in the fine fossil specimens exposed in the Sandwick Fish Bed, and include some of the earliest fish and vascular plants of the fossil record. The rocks at Cruaday Quarry, as elsewhere in Orkney, belong to the Old Red Sandstone group, and were laid down in a harsh arid climate between 350-390 million years ago (during the Devonian Period). At this time the area that is now Scotland lay south of the equator in latitudes equivalent to the present Australian and Kalahari deserts. Deposition of sediment was mainly by large rivers into an enormous freshwater lake (the Orcadian Basin). During the Middle Devonian, the depth of the Orcadian Lake fluctuated and, at times of greatest depth, the central portions of the lake became starved of oxygen (anoxic). It was here that fish carcases were deposited, to become preserved as fossil specimens.
Denwick is located on the north coast of Deerness in the East Mainland. The coastal section at Denwick provides an excellent example of a sequence of glacial deposits in Orkney, which was left as the ice finally retreated about 10,000 years ago. These deposits are collectively known as ‘tills’ (‘till’ is the name given to sediment deposited in direct contact with the glacier) and are important for the following reasons. The scratches on the bedrock (called striations) and the orientation of the rock fragments within the deposits indicate changes in the direction of ice flow during a single glaciation, causing the superimposition of the two distinct till units. The consistent way in which these till units are superimposed, together with the inferred shifts in the direction of the former ice movement, are important strands of evidence when trying to determine the large-scale movements of the ice sheet and its driving forces.
The SSSI at Doomy and Whitemaw Hill in Eday is one of only a few places in Orkney where whimbrel nest. It is also important for Arctic skua. The botanical interest of the site is upland heath, which includes large areas of blanket bog and sandy heath, and provides excellent breeding areas for these bird species.
This site comprises a 62 km stretch of coastline made up of storm beaches, long, sandy bays, seaweed-covered rocks, shingle, mud and two tidal islands. The site is internationally and nationally important for its winter assemblage of wading birds, including turnstone, purple sandpiper, ringed plover, sanderling and bar-tailed godwit. The SSSI has a superb range of habitats for waders. In winter, huge piles of rotting kelp harbour large numbers of sand hoppers and other invertebrates, providing a plentiful food supply. The area is also of international importance as the home of Orkney’s largest common seal colony. Iceland yellowcress, oysterplant and curved sedge are amongst the plants which grow along this coast.
Eynhallow is one of the two most important sites for common seals in Orkney and they use the island both to breed and to haul out. As many as 900 adults have been counted during aerial surveys. The island supports a locally important community of moorland birds and seabirds, including fulmar, Arctic skua, great skua, puffin and black guillemot. There is also an Arctic tern colony. Eynhallow is ringed by shingle and sandy beaches, outcrops of flagstones and cliffs reaching up to 20 metres in height. It is mainly grassy, with areas of heathery heath and tussocks of tufted hair-grass. The rare hart’s tongue fern forms a colony on a rocky outcrop in the ravine that cuts across the island.
Faray and Holm of Faray are two small islands which lie between Westray and Eday and are joined at low tide. The islands are internationally important for their colony of grey seals. The seals use the islands from the beginning of September to the end of November for pupping and breeding. The whole site is important for the seal pups, which move inland after weaning until they have grown their adult coats and go to sea. At other times of the year, adult seals use the islands as a haul-out site, and when they are moulting. The coastline of the islands is mainly rocky with some low cliffs. However, there are several large sandy bays on the west side of Faray. The islands are largely covered by semi-improved grassland, with many tussocks of tufted hair-grass. Iris beds are also found, along with small areas carpeted with sedge.
This site is contained in a valley underlain by Old Red Sandstone rock which was laid down in the Devonian period. It is made up of a rich mosaic of habitats with a complete graduation from acid to alkaline conditions. Glims Moss is considered to be one of the best examples of a raised bog in northern Scotland. It is effectively and inland ‘island’ where, over the millennia, layers of peat have formed a mound that rises above the surrounding landscape. Only specially adapted plants can survive within this enclosed habitat, which is acidic and low in nutrients. They include heather, crowberry, horsetail and wavy hair-grass. At the other end of the valley and the pH scale lies the Dee of Durkadale which is the most northerly example of an alkaline valley marsh (or mire) in Britain and the best example of this habitat found on the Old Red Sandstone of northern Scotland. It is rich in plant life because of the alkaline conditions. The dominant vegetation is a mixture of sedges, mosses and liverworts with lesser tussock sedge where springs occur. Areas of marshy grassland along the Durkadale valley support a wide variety of plants such as mud sedge and white sedge. Moorland birds nesting on the site include hen harrier, merlin and short-eared owl. Hen harriers roost together during the winter and this is one of the three most important sites in Orkney for this spectacular communal activity.
The Holm of Papa Westray is a small low-lying island off the east coast of Papa Westray. It is approximately 1km by 0.3km and rises gradually to a height of 15m at its south-eastern corner. The coastline is mainly rocky with areas of shingle and a small sandy bay at the southern end. The island is home to Britain’s largest breeding colony of black guillemot, with between 120 and 150 pairs. It also regularly attracts as many as 600 non-breeding birds. Other birds which nest on the island include Arctic tern, storm petrel, fulmar, shag, eider duck, lesser black-backed gull, herring gull and great black-backed gull.
The Hoy SSSI is an area of great importance for wildlife, geology and evidence of how Hoy’s landscape has evolved. The features for which it is notified are: its geology and geomorphology; its breeding populations of great skuas, red-throated divers, moorland birds and seabirds; and its diverse habitats which include wet and Montane heath, petrifying tufa springs, woodland and upland heaths. The Hoy SSSI is also a designated SAC and SPA.
This site is an area of Orkney moorland which rises to a height of 221 metres and straddles the north, south and east slopes of Keelylang Hill. The site is nationally important for its gathering of upland breeding birds and especially the variety of birds of prey it supports. These include hen harriers, merlin and short-eared owl. Other birdlife includes curlew, golden plover, snipe, great skua, great black-backed gull, lesser black-backed gull, red grouse, twite, stonechat, wheatear and sedge warbler. The landscape is dominated by blanket bog where heather grows alongside bog cotton and Sphagnum moss. Woodrush and rushes are also found. A feature of Orkney moorland, called dales vegetation, is seen around burns and some of the moorland drains. Richer in nutrients than the surrounding moorland, the dales are carpeted by wild flowers which flourish where only light grazing occurs.
This area of flooded marshland is nationally important for its plant and bird life. Hen harriers are unusual among birds of prey in that they roost together in winter. A large reed bed at Loch of Banks is a favourite roost for around eight hen harriers. Across Britain only 30 to 40 pairs of pintail nest each year, with one pair regularly found on this site. It also supports a large community of breeding wildfowl and waders. These include wigeon, teal, shoveler, mallard, tufted duck, red-breasted merganser, shelduck, mute swan, oystercatcher, ringed plover, dunlin, snipe, curlew, lapwing and redshank. The site contains a mix of reed-bed, open water and wetland. The area is rich in nutrients and supports a wide variety of wetland plants, including the large stand of reeds, willow scrub, creeping willow, sedges, bog-rush, yellow flag iris, branched bur-reed and meadow sweet.
The two largest lochs in Orkney form an important natural heritage site. Harray Loch drains a shallow basin in the centre of the West Mainland. Its waters flow into the Stenness Loch through a narrow channel at Brodgar, which in turn is open to the sea at the Brig o’ Waithe. The waters of the lochs range from marine at the seaward entrance of Stenness to freshwater in Harray with variability between marine and freshwater within Stenness itself. This gives them a rich diversity of plant and animal life. Harray Loch is important for its large number of pondweed species, three of which are nationally scarce. A very rare caddis fly is also found in the loch and it is also the only known site in Scotland for a snail Theodoxus fluviatilis which is commonly found in English rivers. Stenness Loch is the largest brackish water lagoon in the UK and because of its size the salt content of its water varies throughout the loch allowing it to support a range of wildlife suited to marine, brackish and fresh water conditions. Three UK Biodiversity Action Plan priority species of lagoon charophytes have been found here. Both lochs provide an important wintering ground for a wide variety of wildfowl, including pochard, tufted duck, scaup and goldeneye.
Loch of Isbister and The Loons is a naturally eutrophic wetland site in the northwest of the Orkney mainland. The site is of national importance for its botanical and ornithological interest. Formerly the Loch of Isbister was more extensive, but encroachment by peripheral vegetation over thousands of years has resulted in the development of Orkney’s best basin mire complex, with excellent examples of open water transition plant communities. The mosaic of bog habitats supports a very rich assemblage of wetland plants, which include autumnal water-starwort, slender-leaved pondweed and fragrant orchid. The area supports a diverse assemblage of breeding wildfowl including pintail, wigeon, shoveler, snipe, curlew, redshank and lapwing. The site also supports a colony of Arctic tern and about 1% of the British wintering population of Greenland white-fronted goose.
Marwick Head is one of the three biggest seabird colonies in Orkney. The headland is made up of 2km of Old Red Sandstone cliffs, which provide ideal nesting ledges. Birds nesting here include guillemot, kittiwake, puffin, razorbill, fulmar, shag, jackdaw and herring gull. The maritime grassland on the cliff tops is studded with flowers such as thrift, spring squill and kidney vetch. The cliff face by comparison has very little vegetation, with only a few clumps of scurvy grass.
The Mill Bay SSSI is a nationally important site for its Quaternary earth science interest. Mill Bay provides the finest exposure of the ‘shelly till’ which characterises the glacial deposits of Orkney. The Bay site is important because the shell material has the potential, via geochemical dating methods, to aid in determining the timing of the last glaciation of the islands. The erratics (pebbles and boulders derived from far away) and underlying bedrock striations (or scratches) may indicate the general direction of the ice movement. The presence of shells indicates that the ice flowed over the sea bed.
Mill Loch in Eday is one of the best places in Britain to enjoy the sight and sound of red-throated divers. The 10-hectare loch supports one of the densest breeding populations in the UK – with up to 10 pairs nesting each year. The land surrounding the loch is made up of mosses and taller vegetation, making it an ideal nesting site for the divers. Snipe also nest in the wet margins of the loch. The rest of the site is a mosaic of moorland vegetation which includes blanket bog, marshland, wet heath and acidic grassland.
Muckle and Little Green Holms lie 4 km north of Shapinsay and 2 km south of Eday. The site is of outstanding nature conservation interest within the UK for its nationally important breeding colony of breeding grey seals. The vegetation of Muckle Green Holm consists almost entirely of rough pasture with coarse tussocks of tufted hair grass. In addition, a small area of marsh around the valley drains into a lagoon behind the shingle beach at the north-west of the island. Little Green Holm supports rank grassland with high cover of the grass, Yorkshire fog.
The Muckle Head and Selwick SSSI is located on the north coast of the island of Hoy and is nationally important for its Quaternary earth science interest. Both Muckle Head and Selwick represent excellent examples of ‘raised beach’ deposits. These deposits are 6 to 12 metres above present-day sea-level and were formed at a time when the ice caps had melted, and consequently the sea-level was higher. The raised beach deposits underlie a ‘glacial till’ which was deposited during a subsequent glaciation period.
The northern tip of Papa Westray is famous as the place where one of the last great auks was killed in 1813. Today it supports an internationally important Arctic tern colony. There is also a nationally important colony of Arctic skua. The cliffs are home to guillemot, razorbill and kittiwake. Eider duck, oystercatcher, ringed plover and redshank also nest on the site. Narrow strips of clifftop coastal grassland featuring thrift, sea plantain and spring squill give way inland to extensive areas of botanically rich maritime heath. Plants here include Primula scotica, crowberry, ling heather, glaucus sedge and creeping willow. Other notable species include limestone bedstraw, slender-leaved pondweed, Iceland yellow-cress, heath pearlwort, bristle club rush, field gentian, frog orchid, alpine bistort, shoreweed and adder’s tongue.
Made up of four separate areas in the north-east of Sanday, this site contains the largest area of machair outside the Western isles. Machair is one of the rarest habitats in Europe. It is best described as dune pasture that has developed on shell-rich blown sand. Areas of machair are famous for their abundance of wild flowers. Yellow rattle, grass of Parnassus and ragged robin can be found in profusion on this site. Mosses proliferate in wet dune areas and it is the only place in Orkney to find a liverwort called Moerckia hibernica. Amphibious bistort, yellow flag iris and reed canary grass grow in and around lochs. The underlying landforms are integral to the machair interest. Part of the site overlaps a section of the East Sanday Coast SPA, which is home to many species of wader including purple sandpiper, turnstone, bar-tailed godwit, dunlin, sanderling, and grey plover. In winter whooper swan and pintail ducks can be seen on the North Loch. The loch is also one of the best places on the island to see otters.
This SSSI is an area of Orkney moorland famous for its outstanding community of upland birds, in particular the hen harrier. Other breeding birds include merlin, short-eared owl, kestrel, golden plover, dunlin, curlew, redshank, stonechat, wheatear and twite. Blanket bog is the main vegetation in this large area of moorland and there are also stands of tall herbs, ferns and rushes called ‘dales’ vegetation. The blanket bog has an abundance of dwarf shrubs and Sphagnum mosses, while the dales are rich in plants such as wild angelica, winter avens and common valerian. Two nationally scare plants – pyramidal bugle and round-leaved wintergreen have also been seen on the site in the past.
Swona and Muckle Skerry are home to internationally important breeding colonies of Arctic tern. Swona is surrounded by low cliffs, with some caves and offshore stacks. Lush semi-improved grassland is found around the empty houses, while half the island is covered by a grassy maritime heath. A nationally rare eyebright grows on the island, along with oysterplant and two nationally scarce pondweeds. Swona is famous for its herd of wild cattle. Since 1974 they have evolved through natural selection and are now classed as a new and distinct breed – Swona cattle – in the World Dictionary of Livestock Breeds. Low cliffs with numerous geos and small caves also surround Muckle Skerry. The cliffs are topped with maritime grassland. Inland the plant life is dominated by tormentil, common cotton-grass and tufted hair-grass.
This site is made up of two distinct areas, both important for the bird and plant life they sustain. The area around Quendal-Brings and Faraclett forms the second largest coastal heath classed as a SSSI in Orkney. The rest of the site is the third largest area of moorland in the county. The coastal heath supports a colony of Arctic tern and the cliffs are home to guillemot, kittiwake, fulmar, razorbill, puffin, black guillemot and shag. Further inland can be found five species of gull. The heathland supports a nationally important colony of Arctic skua. Arctic skua also nest on the moorland along with red-throated diver, hen harrier, merlin, red grouse, golden plover, dunlin, snipe, curlew, great skua, short-eared owl, stonechat, wheatear and twite. The coastal area of the site forms a rich mosaic of plant life and several colonies of the rare Primula scotica can be found. This area is of national importance for its wide range of plants associated with clifftop maritime grassland, maritime heath and inland heath. The moorland rises to 250 metres and plants on its exposed hilltops are normally found at much higher altitudes elsewhere in Scotland. These include alpine bearberry, alpine saw-wort and dwarf willow. Much of the moorland is covered by blanket bog and wet heath. There are also stands of tall herbs, ferns and rushes called ‘dales’ vegetation. Five nationally scarce plants are found on the moorland. In Orkney three of those – serrated wintergreen, shady horsetail and a hybrid pondweed – can only be found here. The pondweed is found in Muckle Water. Because of its unique nutrient levels this loch is rich in plant life, including some scarce species. It is the only loch of its kind in Orkney.
The cliffs at Yesnaby and the Gaulton coast provide fascinating examples of the Devonian Old Red Sandstone rocks. The Yesnaby cliffs were created from the sand that originally formed dunes around an extensive freshwater lake called Lake Orcadie about 400 million years ago. The fossilised remains of primitive plants that once lived in the lake form small bun-shaped masses of banded rock called stromatolites. The site is particularly noted for a variety called horse-toothed stromatolites. The coastline continues to change through erosion caused by pounding Atlantic breakers and this has led to the formation of a range of features including caves, arches, geos, stacks and shore platforms. Along the cliff-tops, extreme exposure to wind and salt spray has produced some of the best and most extensive areas of maritime grassland and heath anywhere in the UK. Primula scotica (Scottish primrose), red fescue, sea plantain, thrift and spring squill are just some of the plants which carpet the maritime grassland. Further inland, as the sea’s influence reduces, the land gradually develops into first maritime heath and then inland heath. The maritime heath is made up of dwarf shrubs such as common heather, bell heather, crowberry and creeping willow, along with lichens, a variety of grasses, sedges and wildflowers such as mountain everlasting and wild thyme. The site is of interest locally for the birds it supports. These include a pair of peregrine falcons which regularly nest on the sea cliffs. Row Head is noted for its colonies of guillemot and kittiwake. The site also supports small breeding numbers of Arctic skua, great skua and a small colony of Arctic tern.
These two islands lie 60 km to the west of the Orkney mainland and are of international importance for the vast numbers of seabirds they support. Sule Skerry is low-lying and vegetated, whereas Sule Stack is a higher, bare, rock stack with no vascular plants. Scentless mayweed covers the centre of Sule Skerry in summer, where the peaty soil provides ideal burrowing conditions for the nesting puffins. Sule Skerry is home to 58,000 pairs of puffins during the breeding season while Sule Stack supports a colony of around 6,000 pairs of gannets. Both islands are also nesting sites for internationally important colonies of Leach’s petrel, storm petrel and shag. Other seabirds on this site include fulmar, lesser black-backed gull, herring gull, great black-backed gull, kittiwake, Arctic tern, guillemot, razorbill and black guillemot.
Switha is a small, uninhabited, low-lying island which lies 2km east of South Walls and 2km south of Flotta. It has a rocky coastline and is almost totally covered by maritime grassland, with smaller areas of heath and bog. Switha is of outstanding scientific and nature conservation interest within the UK and the EC for its internationally important wintering population of Greenland barnacle geese. This is the third largest wintering population of Greenland barnacle goose in the UK (after Islay and North Uist), and is the most northern nationally important wintering station. The coastline also supports an assemblage of breeding seabirds which include great black-backed gull, cormorant, guillemot, black guillemot, Arctic skua, great skua, fulmar, Arctic tern, shag, herring gull, kittiwake and razorbill. The site is also frequented by otters and grey seals.
Ward Hill Cliffs in South Ronaldsay is a nationally important site for its species-rich lichen heath. It also supports a rich diversity of cliff-top flowering plants in a mosaic of other habitats that include thickly vegetated high cliff slopes, coastal heath, coastal grassland and marshy grassland. The variety of plant life further increases where springs create more calcium-rich conditions. Vegetation on this site grows more luxuriantly than on the more highly exposed cliffs on the western coast of Orkney. The northern part of the site contains the lichen-heath which is made up of a rich mix of heather, bell heather, cross-leaved heath, crowberry, numerous herbs, mosses, liverworts and several species of lichens. Ward Hill Cliffs is also the only known site in Orkney where hemp agrimony can be found, growing amongst tall herbs on sheltered areas of the cliff top. Crowberry and a variety of grasses dominate the coastal heath and the coastal grassland of the southern part of the site. Seabirds, including kittiwake, nest on the cliffs. The base of the cliffs is one of the few breeding sites used by grey seals away from Orkney’s more outlying islands.
Waulkmill is regarded as one of Orkney’s most beautiful beaches. This sheltered sandy bay contains a wide variety of wildlife habitats. The largest saltmarsh in Orkney is found behind a shingle spit at the head of the bay. Covered by the sea at high tide, it has a distinctive flora of plants that tolerate salt, such as sea milk-wort, sea arrow-grass, saltmarsh flat sedge and one-glumed spike-rush. The cliffs that surround the bay support a rich variety of herbs, ferns and shrubs. The only colony of native aspen on the Orkney mainland is found on cliffs on the eastern side of the bay and has a different genetic make-up to aspen found elsewhere in the islands. The cliffs are also one of the best habitats for butterflies and moths in the county. One species of moth, Coloephora vigaureae, has only been seen here. Surrounding the cliffs and saltmarsh are areas of heather moorland and patches of well-developed willow scrub. Wildfowl and waders feed where the burn flows into the bay, while the moorland and scrub provide good habitat for a variety of birds including stonechat.
These moorlands are outstanding for their assemblage of upland breeding birds, in particular red-throated diver which are attracted to the hill lochans, hen harrier and short-eared owl. Other moorland birds which nest on this site include merlin, golden plover, whimbrel, wigeon, lapwing, dunlin, snipe, curlew, Arctic skua, great skua, stonechat, wheatear and ravens. The moorlands are mainly acidic in nature and are made up of wet and dry heaths with large areas of blanket bog. The plant life increases in variety where springs create more alkaline conditions. In these areas, species such as alpine meadow rue and bog rush can be found, along with carpets of brown moss. Abundant communities of tall-herb plants such as wild angelica, valerian, water avens, rose bay willow herb, male fern and buckler fern are found in the sheltered dales. The only trees – mainly eared willow and grey willow – also form patchy scrub in the dales. Other plants include moonwort, frog orchid, twayblade, chickweed wintergreen and hybrid horsetail.
This site follows an 8km stretch of coastline and includes adjacent areas of grassland and heath. The high sea cliffs support populations of breeding kittiwake, guillemot, razorbill, Arctic skua, fulmar, shag, great skua, common gull, herring gull, black guillemot and puffin. A colony of Arctic tern breeds on the coastal heathland behind. There are particularly good examples of species-rich maritime grassland and maritime sedge-heath at the site. These support cliff-top plants such as sea plantain, spring squill and Scottish primrose (Primula scotica). Some of the rocky outcrops support well developed fern communities which include sea spleenwort, brittle bladder fern and male fern.
Further information about each site is also available on the Scottish Natural Heritage website, which can be accessed from the 'Related Sites' section of this web page.