Offshore wind - birds on migration in Scottish waters: strategic review

A report detailing the migratory routes of bird species around the UK and Ireland which have the potential to be impacted by offshore wind developments. This forms part of the strategic study of collision risk for birds on migration and further development of the stochastic collision risk modelling tool work package one.


Introduction

Background

The UK government aims to achieve net zero greenhouse gas emissions by 2050 with a 78% reduction by 2035[1], while the Scottish Government aims to achieve net zero by 2045 with a 75% reduction by 2030[2]. To support this, the offshore wind industry is likely to play a key role in the economy in coming decades, particularly in relation to a green economic recovery as we emerge from the COVID-19 pandemic.

At present, there are 40 operational offshore wind farms or demonstration projects in UK waters (Figure 1), including the world's first floating offshore wind project, and a further 11 which are either under construction or for which consent has been granted[3]. Of these, six operational wind farms and nine which are under construction or for which planning consent has been granted are in Scottish waters[4]. Building on this success, the Crown Estate recently announced six further projects in English and Welsh waters which will deliver almost 8 GW of additional energy, while in Scotland, the ScotWind Leasing Round aims to deliver up to 25 GW of generating capacity[5].

Whilst offshore wind energy offers the potential to mitigate the negative impacts of climate change by reducing carbon emissions from fossil fuels, concerns remain over the potential for negative environmental impacts, particularly in relation to birds (Bradbury et al. 2014; Furness et al. 2013; Huppop et al. 2006). The key impacts associated with offshore wind on birds are believed to be collision with turbines, displacement and barrier effects (Cook et al. 2018; Dierschke et al. 2016; Masden et al. 2009, 2012; Mendel et al. 2019; Thaxter et al. 2019). Prior to consent for a development being granted, the potential for these impacts to negatively affect populations, particularly those of designated features of protected sites, must be considered as part of the Environmental Impact Assessment (EIA) and Habitats Regulations Appraisal (HRA) processes.

Figure 1 Planned, approved and built offshore wind farms in UK waters. Also shown are the potential project sites selected as part of the Round 4 Leasing Round for England, Wales and Northern Ireland, the Plan Option (PO) Areas identified for the ScotWind Leasing Round, and the Agreement Offers announced following the ScotWind Leasing Round[6].
Map of the United Kingdom showing planned, approved and built offshore windfarms as described in text above.

During the breeding season, the UK hosts internationally important populations of seabirds, mostly within a network of protected sites (Mitchell et al. 2004). As a result, much of the development in impact assessment methodology has focussed on tools to assess the potential impact of offshore wind farms on breeding seabirds (Masden, 2015; McGregor et al. 2018; Searle et al. 2018). Of particular note is the development of a stochastic Collision Risk Model (sCRM) which attempts to quantify the uncertainty associated with collision risk estimates (Masden, 2015; McGregor et al. 2018). The model is based on the Band (2012) CRM with input parameters sampled from a range of plausible values, rather than being considered as a single, fixed value.

In addition to hosting internationally important populations of breeding seabirds, UK waters are an important migratory flyway and the UK hosts internationally important populations of waterbirds (swans, geese, ducks, waders and other waterbirds) during the winter (Frost et al. 2021; Wernham et al. 2002). Such species may interact with offshore wind farms during spring and autumn migrations, but also during moult migration (e.g. Green et al. 2021) or in response to cold weather movements. In addition to waterbirds, significant numbers of raptors and passerines may pass through UK waters during migration (Wernham et al. 2002). Consequently, the expansion of the offshore wind industry raises the potential for significant cumulative impacts of offshore wind farms on migratory populations. This may become particularly important given the development of floating turbines which can be placed further offshore, in deeper water areas. In such circumstances, whilst the exposure to breeding seabirds may be substantially reduced, migrating species passing through the area will still be exposed to the risk of collision in relation to these projects, which may lead to concerns at a cumulative scale.

Of particular concern in relation to migrating birds is the potential for individuals to collide with turbines or, for the wind farms to act as a barrier, increasing the distance birds must travel on their migrations (Huppop et al. 2006; Masden et al. 2009, 2012). Evidence from onshore wind farms highlights the response of migrating birds to this risk (Johnston et al. 2014; Villegas-Patraca et al. 2014). There is also emerging evidence of the response of migrating waterbirds to offshore wind farms (Masden et al. 2009; Plonczkier & Simms, 2012) and, evidence of substantial migration across the North Sea at altitudes that would place birds at risk of collision (Fijn et al. 2015). Given that a substantial proportion of migration may take place at night, this may lead to an increased level of collision risk given the potential for migrating birds to be attracted to turbine lighting (Rebke et al. 2019).

The assessment of migrant collision risk differs from that for seabirds as a result of how the flux rate, the number of birds estimated to pass through the turbine rotor swept areas, is calculated. For seabirds, the existing sCRM derives a flux rate based on the density of birds (derived from at-sea surveys) within a wind farm at any given time assuming each bird flies through the wind farm in a straight line at a constant height and speed (McGregor et al. 2018). These assumptions enable the scaling up of the number of birds present in a wind farm at any given point in time to cover the time period over which collision risk is being considered. Following this approach, any given bird may be present within the wind farm multiple times (Band, 2012). In contrast, when assessing migrant collision risk, each individual bird is assumed to pass through any given wind farm only once during each migration season (Band, 2012). The total number of birds passing through the wind farm is estimated by considering the width of the wind farm relative to the width of the migratory corridor for the species concerned, and then multiplying this by the size of the population concerned (Wright et al. 2012; WWT Consulting, 2014).

As part of the National Marine Plan[7], it is Scottish Government policy to ensure that decisions are informed by the best available evidence and make reasonable effort to address any gaps in knowledge. Reflecting this, the Marine Sectoral Plan process and Sustainability Appraisal identified a need to update guidance in relation to migrant collision risk, a need echoed in a NatureScot workshop on marine bird impact assessment guidance[8]. To achieve this, the process for assessing migrant collision risk should be brought into line with that for seabirds. In particular, this should include the potential to incorporate uncertainty into estimates of migrant collision risk. This project will address these gaps in guidance through three work packages:

1. Strategic review of birds on migration in UK waters.

2. Develop stochastic CRM tool for migratory species.

3. Strategic study of collision risk for ScotWind leasing sites for birds on migration in Scottish waters

This report will focus on work package one, originally a strategic review of bird migration in Scottish waters but, subsequently expanded in scope to cover UK waters as a whole.

Scope of Strategic Review of Bird Migration in UK waters

As highlighted above, to support the development of a stochastic collision risk model for migrants, a strategic review of bird migration is required to develop an evidence base with which to underpin this model. Guidance on the use of the model will be available in documentation released alongside it.

Previous reviews of migrant collision risk in relation to offshore wind farms have included both seabird and non-seabird species. For the purposes of this review, we consider that seabird exposure to offshore wind farms will be captured in the density estimates entered into the existing sCRM. Distinguishing between migrant and resident seabirds is not possible. To avoid double-counting of collisions in seabirds, assessment of collision risk of seabirds is best undertaken using the existing model. Consequently, reflecting current policy requirements, the focus of this review is on non-seabird features of Special Protection Areas (SPAs) including swans, geese, ducks, waders, raptors and other non-passerines.

Our review includes species or species populations (hereafter 'species') which are designated features of UK SPAs. For a full list of species considered, see Table 1. Collectively, these species are features of 248 SPAs in the UK (Figure 2; Table 2).

Table 1 Species or species populations considered in strategic review of birds on migration in UK waters

Swans

Geese

Ducks

Waders

Raptors & Owls

Other species

Whooper Swan

Bewick's Swan

Taiga Bean Goose

Pink-footed Goose

'Greenland' White-fronted Goose

'European' White-fronted Goose

'Icelandic' Greylag Goose

'Svalbard' Barnacle Goose

'Greenland' Barnacle Goose

'East Atlantic' Light-Bellied Brent Goose

'Nearctic' Light-Bellied Brent Goose

Dark-bellied Brent Goose

Shelduck

Wigeon

Gadwall

Teal

Mallard

Pintail

Shoveler

Pochard

Tufted Duck

Scaup

Long-tailed duck

Eider

Common Scoter

Velvet Scoter

Goldeneye

Red-breasted Merganser

Goosander

Oystercatcher

Ringed Plover

Golden Plover

Grey Plover

Lapwing

Knot

Sanderling

Purple Sandpiper

Dunlin

Ruff

Snipe

Black-tailed Godwit

Bar-tailed Godwit

Whimbrel

Curlew

Greenshank

Wood Sandpiper

Redshank

Turnstone

Red-necked Phalarope

Dotterel

Avocet

Stone-curlew

Marsh Harrier

Hen Harrier

Montagu's Harrier

Osprey

Merlin

Short-eared Owl

Honey-buzzard

White-tailed Eagle

Great Northern Diver

Black-throated Diver

Red-throated Diver

Bittern

Great Crested Grebe

Slavonian Grebe

Spotted Crake

Corncrake

Nightjar

Figure 2 Special Protection Areas (SPAs) in the UK for which designated features include non-seabird migratory species. The names of these SPAs are given in table 2, and maps highlighting the location of each are given in Appendix 4.
Map of United Kingdom showing Special Protection Areas (SPAs) as referenced in text above and in Appendix 4.
Table 2 Special Protection Areas (SPAs) and proposed SPAs for which the species considered in this review are deignated features. The numbers are carried through to the individual species accounts. Maps giving the location of each SPA are shown in Appendix 4.

1

Abberton Reservoir

55

Rutland Water

109

Cameron Reservoir

163

Mointeach Scadabhaigh

2

Alde-Ore Estuary

56

Salisbury Plain

110

Castle Loch Lochmaben

164

Monach Islands

3

Arun Valley

57

Sandlings

111

Coll

165

Montrose Basin

4

Ashdown Forest

58

Solent and Southampton Water

112

Coll (corncrake)

166

Moray and Nairn Coast

5

Avon Valley

59

Somerset Levels and Moors

113

Creag Meagaidh

167

Muir of Dinnet

6

Benacre to Easton Bavents

60

South Pennine Moors Phase 2

114

Cromarty Firth

168

Muirkirk and North Lowther Uplands

7

Benfleet and Southend Marshes

61

South West London Waterbodies

115

Din Moss - Hoselaw Loch

169

Ness and Barvas Lewis

8

Blackwater Estuary (Mid-Essex Coast Phase 4)

62

Stodmarsh

116

Dornoch Firth and Loch Fleet

170

North Inverness Lochs

9

Bowland Fells

63

Stour and Orwell Estuaries

117

Drumochter Hills

171

North Sutherland Coastal Islands

10

Breckland

64

Tamar Estuaries Complex

118

East Sanday Coast

172

North Uist Machair and Islands

11

Breydon Water

65

Teesmouth and Cleveland Coast

119

Eilean na Muice Duibhe (Duich Moss)

173

Orkney Mainland Moors

12

Broadland

66

Thames Basin Heaths

120

Eoligarry Barra

174

Oronsay and South Colonsay

13

Chesil Beach and The Fleet

67

Thames Estuary and Marshes

121

Fala Flow

175

Otterswick and Graveland

14

Chew Valley Lake

68

Thanet Coast and Sandwich Bay

122

Fetlar

176

Papa Stour

15

Chichester and Langstone Harbours

69

The Swale

123

Firth of Forth

177

Rannoch Lochs

16

Colne Estuary (Mid-Essex Coast Phase 2)

70

The Wash

124

Firth of Tay and Eden Estuary

178

Renfrewshire Heights

17

Crouch and Roach Estuaries (Mid-Essex Coast Phase 3)

71

Thorne and Hatfield Moors

125

Forest of Clunie

179

Rinns of Islay

18

Deben Estuary

72

Thursley Hankley and Frensham Commons (Wealden Heaths Phase 1)

126

Foula

180

River Spey - Insh Marshes

19

Dengie (Mid-Essex Coast Phase 1)

73

Upper Nene Valley Gravel Pits

127

Gladhouse Reservoir

181

Ronas Hill - North Roe and Tingon

20

Dorset Heathlands

74

Walmore Common

128

Glen App and Galloway Moors

182

Rum

21

Dungeness Romney Marsh and Rye Bay

75

Wealden Heaths Phase 2

129

Glen Tanar

183

Shiant Isles

22

East Devon Heaths

76

Falmouth Bay to St Austell Bay

130

Greenlaw Moor

184

Slamannan Plateau

23

Exe Estuary

77

Outer Thames Estuary

131

Gruinart Flats Islay

185

Sléibhtean agus Cladach Thiriodh (Tiree Wetlands and Coast)

24

Foulness (Mid-Essex Coast Phase 5)

78

Solway Firth

132

Hermaness Saxa Vord and Valla Field

186

South Tayside Goose Roosts

25

Gibraltar Point

79

Severn Estuary

133

Hoy

187

South Uist Machair and Lochs

26

Greater Wash

80

The Dee Estuary

134

Inner Clyde Estuary

188

Strath Carnaig and Strath Fleet Moors

27

Hamford Water

81

Liverpool Bay / Bae Lerpwl

135

Inner Moray Firth

189

Switha

28

Holburn Lake and Moss

82

Antrim Hills

136

Inverpolly Loch Urigill and nearby Lochs

190

Tiree (corncrake)

29

Hornsea Mere

83

Belfast Lough

137

Kilpheder and Smerclate South Uist

191

Treshnish Isles

30

Humber Estuary

84

Belfast Lough Open Water

138

Kintyre Goose Roosts

192

West Inverness-shire Lochs

31

Lee Valley

85

Carlingford Lough

139

Knapdale Lochs

193

Wester Ross Lochs

32

Leighton Moss

86

Killough Bay

140

Laggan Islay

194

Westwater

33

Lindisfarne

87

Larne Lough

141

Lairg and Strath Brora Lochs

195

Ythan Estuary Sands of Forvie and Meikle Loch

34

Lower Derwent Valley

88

Lough Foyle

142

Langholm - Newcastleton Hills

196

Bluemull and Colgrave Sounds

35

Marazion Marsh

89

Lough Neagh and Lough Beg

143

Lewis Peatlands

197

Coll and Tiree

36

Martin Mere

90

Outer Ards

144

Loch Ashie

198

East Mainland Coast Shetland

37

Medway Estuary and Marshes

91

Pettigoe Plateau

145

Loch Eye

199

Moray Firth

38

Mersey Estuary

92

Slieve Beagh - Mullaghfad - Lisnaskea

146

Loch Flemington

200

Sound of Gigha

39

Mersey Narrows and North Wirral Foreshore

93

Strangford Lough

147

Loch Ken and River Dee Marshes

201

West Coast of the Outer Hebrides

40

Minsmere-Walberswick

94

Upper Lough Erne

148

Loch Knockie and Nearby Lochs

202

Outer Firth of Forth and St Andrews Bay Complex

41

Morecambe Bay and Duddon Estuary

95

Abernethy Forest

149

Loch Leven

203

Bae Caerfyrddin/ Carmarthen Bay

42

Nene Washes

96

Achanalt Marshes

150

Loch Lomond

204

Berwyn

43

New Forest

97

Aird and Borve Benbecula

151

Loch Maree

205

Burry Inlet

44

North Norfolk Coast

98

Arran Moors

152

Loch of Inch and Torrs Warren

206

Dyfi Estuary / Aber Dyfi

45

North Pennine Moors

99

Assynt Lochs

153

Loch of Kinnordy

207

Elenydd - Mallaen

46

North York Moors

100

Beinn Dearg

154

Loch of Lintrathen

208

Migneint-Arenig-Dduallt

47

Northumbria Coast

101

Ben Alder

155

Loch of Skene

209

Northern Cardigan Bay / Gogledd Bae Ceredigion

48

Ouse Washes

102

Ben Wyvis

156

Loch of Strathbeg

210

Traeth Lafan/ Lavan Sands Conway Bay

49

Pagham Harbour

103

Black Cart

157

Loch Ruthven

211

Skomer Skokholm and the Seas off Pembrokeshire / Sgomer Sgogwm a Moroedd Penfro

50

Peak District Moors (South Pennine Moors Phase 1)

104

Bridgend Flats Islay

158

Loch Shiel

212

Scapa Flow

51

Poole Harbour

105

Caenlochan

159

Loch Spynie

213

North Orkney

52

Porton Down

106

Cairngorms

160

Loch Vaa

53

Portsmouth Harbour

107

Caithness and Sutherland Peatlands

161

Lochnagar

54

Ribble and Alt Estuaries

108

Caithness Lochs

162

Lochs of Spiggie and Brow

Other Important Aggregations

214

Orkney Mainland (Greylag Geese)

pSPA

215

East Coast Marine

To build the evidence base with which to assess collision risk for each of the 70 target species, we conducted literature searches, data extraction and analyses to acquire information on:

  • Population estimates;
  • Migratory routes;
  • Timing of migration;
  • Migratory flight heights;
  • Migratory flight speeds;
  • Avoidance behaviour and rates.

Finally, we consider the overall potential for climate change to alter migrant species' exposure to collision risk.

Contact

Email: ScotMER@gov.scot

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