Abstract
This report describes the results of the T-0 surveys for the monitoring of seabirds in relation to the future Offshore Wind Farm ‘Gemini’. This wind farm, or rather two twin wind farms, will be built in the near future on the eastern Dutch Continental Shelf, close to the Dutch/German offshore border, at some 55 km north of the island Schiermonnikoog. In order to describe year-round seabird presence and densities and to assess which species are most likely to be affected by the future wind farm (and at which time of year), year-round, monthly seabirds surveys were carried out in and around the future wind farms. The site is close to German waters (where other wind farms may be built) and close to a major shipping route (where surveying for seabirds is logistically difficult and where other disturbing factors are at play). Therefore, a survey design was chosen with a total survey area that was relatively narrow and which runs parallel (but outside) the shipping lane. The two wind farms are situated centrally in the study area, with three circa 15 km long stretches of reference areas in the west, centrally, and to the east of the wind farms (Figures 1 & 2). The principal research question for these T-0 surveys is: ‘How are seabirds distributed in the general area, in the absence of wind farms?’ The study aimed to map year-round seabirds’ presence, numbers, and distribution of all species involved, and to identify the times of year during which different species use the area mostly or are largely absent. While we note that only one year of T-0 data cannot consider year to year variation in seabird presence, the general seasonal patterns found allow recommendations for optimal timing of future (T-1) surveys, which we think would give the best value for money. With the exception of the Common Guillemot (Uria aalge), most seabirds do not reach high densities in the Gemini area, and therefore, the Gemini wind farms are unlikely to significantly impact these birds. Breeding birds, from protected colonies on Helgoland and on Dutch and German Wadden Islands, did not reach high densities during any of the spring and summer surveys. Migrant birds were not noted in high numbers. Common Guillemots were the most numerous birds, reaching high densities during their post-breeding exodus (from UK colonies, presumably) and over the autumn and winter. As Common Guillemots are known to be displaced to some extent by offshore wind farms, the Gemini lay-out will allow for a very useful T-1 study that, together with similar T-1 studies in other offshore wind farms, will help the decision process for further offshore wind development.