Abstract from BTO Research Report No. 419:

A.N. Banks, I.M.D. Maclean, N.H.K. Burton, G.E. Austin, N. Carter, D.E. Chamberlain, C. Holt & M.M. Rehfisch (2005)

The Potential Effects on Birds of the Greater Gabbard Offshore Wind Farm Report for February 2004 to March 2005. ISBN 978-1-906204-04-4

Executive Summary

1. Greater Gabbard Offshore Winds Ltd (GGOWL) propose to build an offshore wind farm adjacent to two sandbank areas 23 km off the Suffolk coast, known as the Inner Gabbard and Galloper. The wind farm project is known as Greater Gabbard.
2. GGOWL has contracted the British Trust for Ornithology (BTO) and Environmentally Sustainable Systems (ESS) to undertake surveys and to assess the impacts of the proposed wind farm on bird populations.
3. The North Sea and Suffolk coast are important areas for many waterbirds including divers, seaducks, gulls and auks.
4. Offshore surveys were carried out between February 2004 and March 2005 to ascertain the abundance and distribution of birds in the “footprint” area of the proposed wind farm, plus an extended “reference” survey area. Aerial and boat surveys were used in accordance with COWRIE recommendations. Surveys are ongoing.
5. Onshore breeding birds at Sizewell were surveyed using a six-visit, mapping methodology approach, with visits from late March to late June. Territory analyses were carried out for species of conservation importance and other species likely to be affected by construction work were identified. The results from the survey were supplemented with records from local and national bird surveys and the Suffolk Bird Report.
6. Distance sampling techniques were employed to generate accurate estimates of bird abundance for the two offshore study areas, whilst smoothed surfaces of distribution were obtained using GIS kriging methods.
7. Seventeen principal offshore species were analysed according to conservation designation or national or regional importance, and species accounts are presented in the context of breeding season, wintering season and migration periods.
8. No species were found in numbers estimated to exceed the 1% international population threshold. Three species (Red-throated Diver, Great Skua and Lesser Black-backed Gull) were estimated to occasionally exceed the 1% national population threshold in either the breeding or wintering season, within the entire study area covered (footprint plus reference area), an area approximately five times greater than the proposed wind farm footprint.
9. Six further species (Northern Fulmar, Northern Gannet, Mew Gull, Herring Gull, Great Blackbacked Gull and Black-legged Kittiwake), plus the species group containing auks, were estimated to exceed the 1% regional population threshold in either the wintering or breeding season, within the entire study area covered (footprint plus reference area). Regional importance is based on the aerial surveys of the Outer Thames Estuary carried out during the winter of 2004/05.
10. Proportional estimates of offshore bird numbers within the wind farm footprint are low, with no species exceeding the 1% national importance threshold and only three species exceeding the 1% regional threshold.
11. Offshore distribution of most species was broadly evenly spread, except for large feeding flocks of gulls, often found near the southern wind farm footprint area.
12. Boat-based surveys of migrants detected few birds passing through the study area, with Starlings the only species identified in numbers greater than 51.
13. Modelling revealed no conclusive relationships between bird numbers and the available environmental data.
14. Onshore surveys revealed a number of birds of conservation importance in a study area that included the beach at Sizewell and fields around the cable route and proposed substation, including Wood Lark and Cetti’s Warbler. However, small numbers of territories were identified for most species.
15. There is little abundance or distributional evidence to suggest that the wind farm area is of more than regional importance for marine bird species.
    

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