Therkildsen, O.R, Petersen, I.K., Balsby, T.J.S., Nielsen, R.D., Bladt, J., Bisschop-Larsen, R., Pedersen, C.L., Sterup, J. & Nielsen, J.C. 2021. Vurdering af den potentielle påvirkning af fugle ved opstilling af to vindmølleparker i Øresund. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 130 s. - Teknisk rapport nr. 238.
DCE - National Center for Energy & Environment, Aarhus University, was commissioned by HOFOR to investigate the potential impacts on bird populations in relation to two proposed offshore windfarms in Øresund. The two windfarms will be placed east of Saltholm (Nordre Flint Windfarm) and between Amager, Stevns and Falsterbo (Aflandshage Windfarm).
Here we present the results of our pre-construction investigations, which were carried out from spring 2019 to autumn 2020, together with an assessment of the potential impacts of the two proposed windfarms on bird populations occurring in the study area.
We focused on species for which nearby Special Protection Areas have been designated and other bird species of high conservation interest, i.e. bird species listed on Annex 1 of the EU Birds Directive and other regularly occurring migratory species. On this basis a number of raptors and common crane were included in the investigations.
We aimed at generating species-specific data, whenever this was technically possible. We used visual transect counts, laser range finder data, horizontal radar and aerial surveys, which in combination provided the basic information for the ornithological assessment.
From the results of the pre-construction investigations, the species for which we estimated that more than one annual collision with wind turbines at Nordre Flint Windfarm would take place were barnacle goose (62), cormorant (37), common crane (6), common eider (6), greylag goose (3) and common buzzard (2).
Likewise, the species for which we estimated that more than one annual collision with wind turbines at Aflandshage Windfarm would take place were cormorant (40), barnacle goose (15), common eider (13), common crane (12) and greylag goose (6).
For all of these species, a high proportion of individuals passing the study area did so at rotor height. Nevertheless, this still only resulted in a relatively limited number of predicted collisions even for these species. For the remainder of the species included in the pre-construction investigations, we predicted that the annual number of collisions would be less than one.
Common eider and red-breasted merganser were the only two species occurring in relatively high numbers around the two wind farms and for which we estimated that more than 25 individuals would be displaced. We estimated that up to 749 common eiders would be displaced from Nordre Flint Windfarm in March, whereas 88 red-breasted mergansers would be displaced in February. This corresponds to 2.1% and 1.6% of a total of 36,000 common eiders and 5,700 red-breasted mergansers present in Øresund in March and February, respectively. For all species, the degree of displacement expected from Aflandshage Windfarm Vindmøllepark was assessed to be of a smaller magnitude.
On the basis of the overall assessment, we consider the potential impacts of the two windfarms on the bird populations occurring in the study area unlikely to be significant. Likewise, we consider the contribution of the two proposed windfarms to the cumulative impact of human activity unlikely to be significant.
It is important to keep in mind that the data collected during the pre-construction investigations only covers a relatively short time period. We are therefore cautious when we assess the extent to which there may be year-to-year variation in the occurrence of birds. Although this is not likely to affect our conclusions, we stress that different weather conditions can affect flight behaviour and migration pathways, whereas severe weather conditions may increase collision risk and lead to situations different from the general patterns we have described here.
