VULNERABILITY OF SCOTTISH SEABIRDS TO OFFSHORE WIND

3.5 Disturbance by wind farm structures, ship and helicopter traffic (Factor 5)

Seabird species vary in their reactions to offshore wind turbines, ship and helicopter traffic such as occurs during maintenance of offshore wind farm turbines. Where possible, scores presented by Garthe and H◘ppop (2004) were used, adjusted where appropriate where more recent studies have been published. A literature search was carried out focused on disturbance sensitivity of seabird species, and scores allocated to species were moderated by experts. Scoring categories were: 1 (hardly any escape behaviour and a very short flight distance when approached), to 5 (strong escape behaviour, at a large response distance). Although disturbance distances have often been reported as relatively short (Barrett and Vader 1984, Evans and Nettleship 1985, Carney and Sydeman 1999, Thayer et al. 1999, Rojek et al. 2007, Garthe and H◘ppop 2004), alcids (e.g. common guillemots, razorbills, puffins) can sometimes be disturbed by boats hundreds of metres away (Ronconi and Clair 2002, Bellefleur et al. 2009). Divers are especially sensitive to approaching boats and may dive or fly off when vessels are more than 1000m away (Schwemmer et al. 2011, Topping and Petersen 2011). Among the sea ducks, scoters are particularly vulnerable to being disturbed by boats (Kaiser et al. 2006, Schwemmer et al. 2011). Greater scaup dive or hide when low-flying helicopters approach (Austin et al. 2000), and are disturbed by passing ships up to 400m away (Platteeuw and Beekman 1994). Common eider had a 208m median flush distance from ships, but with no reaction from some flocks on the water (Schwemmer et al. 2011). Long-tailed ducks had a 293m median flush distance from ships (Schwemmer et al. 2011). In contrast, common scoter had a 804m median flush distance from ships, and a maximum flush distance of 3.2km (Schwemmer et al. 2011). Kaiser et al. (2006) reported that common scoter had flush distances of 1000-2000m, somewhat longer distances than reported by Schwemmer et al. (2011). Goldeneyes fly from ships passing at 500-1000m away (Platteeuw and Beekman 1994). Terns can be followed at a moderate distance by a small inflatable boat without apparently causing significant disturbance (Perrow et al. 2011), while some seabirds such as fulmars and shearwaters, appear to show little or no disturbance response to boats, and little response to aircraft. While it is clear that some seabirds do strongly avoid wind turbines at sea, recent work modeling the cumulative impact of disturbance by wind turbines suggests that the impact of these through increased travel distances and habitat loss is trivial, even for species that show especially strong avoidance behaviour, such as red-throated divers (Topping and Petersen 2011).

Table 9. Disturbance scores