Capsule No obvious effects were detected, except for reduced Cormorant Phalacrocorax carbo presence after construction.
Aim To check for differences in the numbers and behaviour of seabirds following construction of two turbines 1 km offshore.
Methods Shore‐based two‐hour watches were conducted several times per month during 26 months before turbine construction, seven months during construction, and 32 months after construction. Numbers, flight heights and directions of all passing seabirds were noted, as were weather and tidal conditions. No watches were made under darkness or in poor daytime visibility.
Results In summer, numbers of Cormorants declined post‐construction, while Sandwich Terns Sterna sandvicensis and Great Black‐backed Gulls Larus marinus increased. Otherwise no meaningful changes in bird numbers and behaviour were recorded, and no collision mortality was witnessed during 352 hours of daytime watches post‐construction. Most seabirds flew below the height of the rotor blades.
Conclusion Apart from possibly causing decline in summer usage of the locality by Cormorants, the turbines seem to have had no adverse effects on the local seabirds in the periods and conditions covered by our watches. We advise against extrapolating our findings to conditions of poor visibility or darkness, or to larger windfarms.