BTO Research Report No. 419 The Potential Effects on Birds of the Greater Gabbard Offshore Wind Farm Report for February 2004 to March 2005 Authors A.N. Banks, N.H.K. Burton, G.E. Austin, N. Carter, D.E. Chamberlain, C. Holt & M.M. Rehfisch British Trust for Ornithology, The Nunnery, Thetford, IP24 2PU E. Wakefield & P. Gill Environmentally Sustainable Systems Ltd., 130 St. Stephen Street, Stockbridge, Edinburgh EH3 5AD Ornithological Baseline Report and Environmental Impact Assessment produced by the British Trust for Ornithology and Environmentally Sustainable Systems Limited under contract to Project Management Support Services Limited on behalf of Greater Gabbard Offshore Winds Limited. October 2005 British Trust for Ornithology, The Nunnery, Thetford, Norfolk, IP24 2PU Registered Charity No. 216652 CONTENTS Page No. List of Tables...........................................................................................................................................5 List of Figures .........................................................................................................................................8 List of Appendices................................................................................................................. 10 EXECUTIVE SUMMARY..................................................................................................................11 1. INTRODUCTION.................................................................................................................13 1.1 Objectives ..............................................................................................................................13 1.2 Definition of the Study Areas...............................................................................................13 1.3 Species and Conservation Designations..............................................................................17 1.4 Consultations.........................................................................................................................20 2. SURVEY METHODS...........................................................................................................21 2.1 Offshore Survey Methods.....................................................................................................21 2.1.1 Boat Surveys...........................................................................................................21 2.1.1.1 Sampling strategy...............................................................................................21 2.1.1.2 Sampling methods ..............................................................................................22 2.1.2 Aerial surveys.........................................................................................................23 2.2 Onshore survey methods ......................................................................................................25 3. DATA ANALYSIS................................................................................................................27 3.1 Offshore data analysis ..........................................................................................................27 3.1.1 Abundance estimates: distance sampling............................................................27 3.1.2 Distribution: smoothed interpolation ..................................................................28 3.2 Onshore data analysis...........................................................................................................28 4. OFFSHORE: SPECIES ACCOUNTS ................................................................................29 4.1 Offshore species accounts: selection criteria ......................................................................29 4.1.1 National and Regional importance ......................................................................29 4.1.2 Species of principal concern .................................................................................32 4.2 Red-throated Diver ...............................................................................................................34 4.2.1 Boat surveys ...........................................................................................................34 4.2.2 Aerial surveys.........................................................................................................34 4.2.3 The importance of the Greater Gabbard for Red-throated Divers through the year.........................................................................................36 4.2.3.1 Winter and Summer............................................................................................36 4.2.3.2 Migration............................................................................................................36 4.3 Black-throated Diver ............................................................................................................42 4.3.1 Boat surveys ...........................................................................................................42 4.3.2 Aerial surveys.........................................................................................................42 4.3.3 The importance of the Greater Gabbard for Black-throated Divers through the year.........................................................................................43 4.3.3.1 Winter and Summer............................................................................................43 4.3.3.2 Migration............................................................................................................43 4.4 Northern Fulmar...................................................................................................................44 4.4.1 Boat surveys ...........................................................................................................44 4.4.2 Aerial surveys.........................................................................................................45 October 2005 1 Page No. 4.4.3 The importance of the Greater Gabbard for Northern Fulmar through the year.......................................................................................46 4.4.3.1 Winter and Summer............................................................................................46 4.4.3.2 Migration............................................................................................................47 4.5 European Storm Petrel.........................................................................................................52 4.5.1 Boat surveys ...........................................................................................................52 4.5.2 Aerial surveys.........................................................................................................52 4.5.3 The importance of the Greater Gabbard for European Storm Petrel through the year..............................................................................52 4.5.3.1 Winter and Summer............................................................................................52 4.5.3.2 Migration............................................................................................................52 4.6 Northern Gannet...................................................................................................................53 4.6.1 Boat surveys ...........................................................................................................53 4.6.2 Aerial surveys.........................................................................................................54 4.6.3 The importance of the Greater Gabbard for Northern Gannet through the year.......................................................................................55 4.6.3.1 Winter and Summer............................................................................................55 4.6.3.2 Migration............................................................................................................56 4.7 Common Scoter.....................................................................................................................61 4.7.1 Boat surveys ...........................................................................................................61 4.7.2 Aerial surveys.........................................................................................................61 4.7.3 The importance of the Greater Gabbard for Common Scoter through the year.........................................................................................62 4.7.3.1 Winter and Summer............................................................................................62 4.7.3.2 Migration............................................................................................................62 4.8 Great Skua ............................................................................................................................64 4.8.1 Boat surveys ...........................................................................................................64 4.8.2 Aerial surveys.........................................................................................................65 4.8.3 The importance of the Greater Gabbard for Great Skua through the year...........................................................................................65 4.8.3.1 Winter and Summer............................................................................................65