VULNERABILITY OF SCOTTISH SEABIRDS TO OFFSHORE WIND
The project considers the vulnerability of seabird species to interactions (collision and displacement) with offshore wind farms.
3.6 Flexibility in habitat use (Factor 6)
Seabirds vary in the range of habitats they use, and whether they use these as specialists or generalists. Habitats at sea include a range of different oceanographic conditions, for example relating to water masses and frontal systems. This score classifies species into categories from 1 (use a wide range of habitats over a large area, and usually with a relatively wide range of foods) to 5 (specialise in using a very limited and predominantly inshore habitat, and generally with a narrow focus on a particular food). Species scoring low tend to forage over large marine areas with little association with particular marine features. Species scoring high tend to feed on very specific habitat features, such as shallow banks with bivalve communities, or kelp beds. Where available, scores presented by Garthe and H◘ppop (2004) were used. Scores for other species were based on foraging ecology described in single species studies in the literature, or from standard handbook descriptions.
Literature indicates many cases of species showing limited flexibility in feeding habitat. For example, greater scaup switch feeding sites and species according to prey availability (Nilsson 1970), but need shallow water areas for foraging, as do common goldeneyes (Jones and Drobney 1986). Common eiders, long-tailed ducks and common scoters are dependent on shallow feeding grounds with shellfish banks (Garthe 2006). Long-tailed ducks are dependent on shallow feeding grounds with shellfish banks (Garthe 2006). Red-throated diver wintering range was considered on the basis of diet studies to be restricted to nearshore, shallow marine waters (Guse et al. 2009). However, Garthe (2006) concluded from at-sea surveys that red-throated divers are not dependent on shallow feeding grounds as they are not restricted to shellfish banks, and they are not restricted to nearshore waters in the German sector of the North Sea (Garthe 2006). The same applies to black-throated divers in winter (Garthe 2006). Both species apparently avoid shipping lanes as they appear not to habituate to disturbance from ships (Schwemmer et al. 2011).
Table 10. Flexibility in habitat use by seabirds scores
| Species | Reference | Score |
|---|---|---|
| Greater scaup | Nilsson 1970 (able to switch feeding sites and species according to prey availability, but limited to very specific habitat); Jones and Drobney 1986 (need shallow waterareas); Forrester et al. 2007 (winters in sheltered sea lochs and firths, brackish coastal lagoons and freshwater lochs close to the coast where molluscs are available in shallow water - much less than 10m deep) | 4 |
| Common eider | Garthe and H◘ppop 2004 gave score 4; Garthe 2006(dependent on shallow feeding grounds with shellfish banks) Forrester et al. 2007 (almost entirely coastal, mainly in sheltered and shallow bays where blue mussel beds arepresent) | 4 |
| Long-tailed duck | Garthe 2006 (dependent on shallow feeding grounds with shellfish banks); Forrester et al. 2007 (mainly along sheltered coasts, usually with sandy substrates) | 4 |
| Common scoter | Garthe and H◘ppop 2004 gave score 4; Garthe 2006 (dependent on shallow feeding grounds with shellfish banks); Forrester et al. 2007 (shallow sea with soft substrates, where molluscs are available in depths 10-20m) | 4 |
| Velvet scoter | Garthe and H◘ppop 2004 gave score 4; Forrester et al. 2007 (exclusively at sea, from close inshore to well offshore, in both sheltered estuaries and off exposed coasts, commonly feeding in depths of ca 15m but capable of diving to 30m which can enable birds to spend time over underwater banks far enough offshore to be invisible from land) This suggests a lower score than given by Garthe and H◘ppop 2004 since habitat use by this species seems to be wider than in common scoter, for example. | 3 |
| Common goldeneye | Jones and Drobney 1986 (need shallow water areas); Forrester et al. 2007 (freshwater lochs, rivers, coastal lagoons, estuarines and open coast, but in marine areas needs molluscs or crustaceans in shallow water, often aggregates around sewage outfalls) | 4 |
| Red-throated diver | Garthe and H◘ppop 2004 gave score 4; Guse et al. 2009 (wintering range restricted to nearshore, shallow marine waters - shown by diet); Garthe 2006 (not dependent on shallow feeding grounds as they are not restricted to shellfish banks - not restricted to nearshore waters Germany); Forrester et al. 2007 (prefers inshore waters often with someshelter, most regularly being found in sounds and wide sandybays) | 4 |
| Black-throated diver | Garthe and H◘ppop 2004 gave score 4; Garthe 2006 (not dependent on shallow feeding grounds as they're notrestricted to shellfish banks - not restricted to near shorewaters Germany); Forrester et al. 2007 (inshore , favouring certain widely scattered relatively shallowand predominantly sandy-bottomed sites) | 4 |
| Great northern diver | Forrester et al. 2007 (coastal marine waters, found in sheltered sandy bays, but equally at home around stormy headlands, often as much as 10km offshore, coming closer to shore during periods of bad weather), so lower score than for other diver species seems probably appropriate; reviewers suggested a score of 4 for this species might be appropriate. | 3 |
| Great-crested grebe | Garthe and H◘ppop 2004 gave score 4; Forrester et al. 2007(some stay on breeding freshwaters, but most move tosheltered estuaries for winter) | 4 |
| Slavonian grebe | Forrester et al. 2007 (sheltered shallow coastal waters,especially estuaries and bays) | 4 |
| Northern fulmar | Garthe and H◘ppop 2004 gave score 1; Forrester et al. 2007(oceanic, preferred marine habitat around Scotland is the shelf-break areas to the north and west, although very large numbers can occur near trawler fleets elsewhere over the continental shelf) | 1 |
| Sooty shearwater | Forrester et al. 2007 (oceanic, generally prefers cold pelagic waters) | 1 |
| Manx shearwater | Forrester et al. 2007 (pelagic although mainly over continental shelf; range over most of the North Atlantic continental shelf in summer) | 1 |
| European storm-petrel | Forrester et al. 2007 (pelagic, generally found over the continental shelf) | 1 |
| Leach's storm-petrel | Forrester et al. 2007 (oceanic, found above and beyond the shelf break over deep water) | 1 |
| Northern gannet | Garthe and H◘ppop 2004 gave score 1; Forrester et al. 2007(oceanic, pelagic but mainly inshore over continental shelf) | 1 |
| Great cormorant | Garthe and H◘ppop 2004 gave score 3; Forrester et al. 2007(may visit a variety of freshwater habitats, in winter distributed more evenly around coasts, especially sea lochs,estuaries and firths) | 3 |
| Shag | Watanuki et al. 2008 ('flexible foraging strategy' - use of both sandy and rocky areas); Wanless et al. 1991b (recorded feeding between 1-60m and over many sediment categories (rock, sand, gravel, mud) - generally avoided deep and muddy sediment areas. Mostly inshore but within that area the species is fairly plastic in its requirements) | 3 |
| White-tailed eagle | Forrester et al. 2007 (both inland and coastal habitats, including estuaries, moorland, agricultural land, marshes and lochs, and rocky shore coasts) | 2 |
| Arctic skua | Garthe and H◘ppop 2004 gave score 2; Forrester et al. 2007 (coastal shelf seas) | 2 |
| Great skua | Garthe and H◘ppop 2004 gave score 2; Forrester et al. 2007 (shallow seas over continental shelf, large numbers associating with fishing vessels) | 2 |
| Black-headed gull | Garthe and H◘ppop 2004 gave score 2; Forrester et al. 2007 (coastal and inland in winter, including beaches, estuarine mudflats, inland on grass and freshly ploughed land, refuse tips, lochs and estuaries) | 2 |
| Common gull | Garthe and H◘ppop 2004 gave score 2; Forrester et al. 2007 (coastal and inland in winter, feeding on farmland, playingfields, estuaries and at sea) | 2 |
| Lesser black-backedgull | Garthe and H◘ppop 2004 gave score 1; Forrester et al. 2007 (feeds in a range of habitats in coastal areas, and in agricultural areas, and extensive use is made of refuse tips and other sources of human waste; generally uses more marine areas than herring gull) | 1 |
| Herring gull | Garthe and H◘ppop 2004 gave score 1; Forrester et al. 2007 (diet is catholic, taking live marine and terrestrial prey and scavenging. Forages around ships in inshore areas, on shoaling fish, in the intertidal zone, in agricultural areas, on refuse and in streets) | 1 |
| Great black-backed gull | Garthe and H◘ppop 2004 gave score 2; Forrester et al. 2007 (forages at sea and on estuaries, beaches and rocky coasts and on islands that often hold seabird colonies. Less common inland than other large gulls) | 2 |
| Black-legged kittiwake | Garthe and H◘ppop 2004 gave score 2; Kotzerka et al. 2010 (birds foraged over the continental shelf within the 200m depth contour. Some evidence they may forage over deepwater areas. Likely to be seasonal changes) Forrester et al. 2007 (extremely pelagic) | 2 |
| Little tern | Forrester et al. 2007 (extremely coastal, usually sheltered shallow marine or estuarine feeding areas) | 4 |
| Sandwich tern | Garthe and H◘ppop 2004 gave score 3; Forrester et al. 2007 (inshore waters on all coasts, but particularly those with shallow water and sandy bottoms such as estuaries) | 3 |
| Common tern | Garthe and H◘ppop 2004 gave score 3; Forrester et al. 2007 (in Scotland mainly in estuaries, some on sea lochs and more open but sheltered coasts, few inland on rivers and lochs) | 3 |
| Roseate tern | Forrester et al. 2007 (the most marine of the Sterna terns, but in Scotland mostly occurs in Firth of Forth estuary) | 3 |
| Arctic tern | Garthe and H◘ppop 2004 gave score 3; Forrester et al. 2007 (coastal marine) | 3 |
| Common guillemot | Garthe and H◘ppop 2004 gave score 3; Forrester et al. 2007 (typically feeds offshore with inshore and pelagic feeding less common) | 3 |
| Razorbill | Garthe and H◘ppop 2004 gave score 3; Forrester et al. 2007(found in a wide range of marine habitats but generally inshallow sea) | 3 |
| Black guillemot | Forrester et al. 2007 (exclusively coastal, usually feeds inshore, close to breeding sites, often associating with kelpbeds) | 4 |
| Little auk | Forrester et al. 2007 (an oceanic plankton feeder, occurringmainly offshore) | 2 |
| Atlantic puffin | Garthe and H◘ppop 2004 gave score 3; Forrester et al. 2007 (feeds far from the coast and is pelagic in winter) | 3 |
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