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 Ltd. (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 April 2006 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.
5. 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.
6. Thirty-two principal 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.
7. No species were found in numbers estimated to exceed the 1% international population threshold. Four species (Red-throated Diver, Great Skua, Lesser Black-backed Gull and Great 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.
8. Five further species (Northern Fulmar, Northern Gannet, Mew Gull, Herring 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.
9. Proportional estimates of offshore bird numbers within the wind farm footprint are low, with only Red-throated Diver exceeding the 1% national importance threshold and only four species, Fulmar, Herring Gull, Great Black-backed Gull and Kittiwake (and also Auks) exceeding the 1% regional threshold. However the threshold for Red-throated Diver is probably too low.
10. 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 and additionally in the northeast of the survey after May 2005.
11. The presence of this additional gull flock resulted in most gull species being recorded in greater numbers during the later survey period (May 2005 – April 2006) than in the earlier period of survey (February 2004 – March 2005). Red-throated Diver were also more abundant during the second survey period, but auk species declined in abundance between the two survey periods.
12. Boat-based surveys of migrants detected few birds passing through the study area, with Starling the only species identified in numbers greater than 51.
13. Modelling on data collected during the first survey period (February 2004 to March 2005) revealed no conclusive relationships between bird numbers and the available environmental data. Consequently such modelling was not attempted on data collected during the second survey period.
14. 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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