Therkildsen, O.R., Balsby, T.J.S., Nielsen, R.D., Bladt, J. & Bisschop-Larsen, R. 2019. To vindmølleparkers virkninger på fugle og betydningen for flytrafikken i Københavns Lufthavn. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 82 s. - Teknisk rapport nr. 157. http://dce2.au.dk/pub/TR157.pdf
DCE - National Center for Energy & Environment, Aarhus University, was commissioned by HOFOR to investigate the potential impacts on bird migration in relation to two proposed offshore windfarms in Øresund and their potential impacts on flight safety, regularity and capacity at Copenhagen Airport.
Here we present the results of our pre-construction investigations carried out during spring and autumn 2019 and an assessment of the potential impacts of the proposed windfarms on the overall flight patterns and behavior of relevant birds species occurring in the area throughout the year. We used current knowledge from the literature on avoidance behavior of birds in relation to offshore windfarms to assess the extent to which any changes might affect flight safety, regularity and capacity at Copenhagen Airport. This stage of the pre-construction investigations focused on potential impacts on flight safety from the proposed windfarms, whereas the next phase will comprise a final assessment of the potential impacts of the two windfarms on bird populations occurring in the area.
From the literature, it is evident that in most cases birds avoid offshore windfarms by flying horizontally around the turbines. Birds passing an offshore windfarm may also change their flight altitude, but only rarely to an extent that causes more birds to fly above turbine height. As an exception to the general pattern, we identified common buzzard as the only species, which may show vertical avoidance to an extent that might lead to more individuals being present above turbine height during migration.
Since the two windfarms are not to be placed on important migration corridors, their presence will only affect a smaller proportion of the total number of birds migrating through the area. Although local breeding, staging and wintering bird populations perform daily flights between night roosts and feeding areas, these movements typically occur at low flight altitude and we consider the presence of the two windfarms unlikely to affect the overall flight patterns in the area. Some species, i.e. cormorant and gulls, may show some degree of attraction to windfarms. However, our investigations showed that for these species, local movements occur at low flight altitudes and as a result are unlikely to affect flight safety. Other species, i.e. some terns and common eider, are hardly affected by offshore wind farms and accordingly no changes in flight patterns in the area are likely to occur.
On the basis of our field studies and current knowledge from literature we consider the potential impacts on bird migration patterns and flight behavior from the two proposed windfarms unlikely to be significant. This also applies to the bird species identified as high-risk species by the airport, i.e. local breeding populations, including barnacle goose and cormorant, moulting greylag geese and migrating geese, raptors and common crane. Accordingly, it is unlikely that the presence of the two windfarms will have any significant impact on flight safety at Copenhagen Airport.
