Interactions between offshore wind farms and marine wildlife, especially seabirds, could lead to negative impacts (such as mortality associated with collision and/or displacement) on populations. It is therefore crucial to predict and identify such risks in order to limit them at every step of wind farm projects (prospecting, construction, operation, maintenance and decommissioning). But how can we study seabird behaviour and wind turbine impacts when numerous species spend most of their annual cycle far away offshore? Direct observations at wind turbine sites are limited and not always adapted for future predictions. Modelling is therefore a useful tool to calculate the theoretical number of seabirds that might collide with the turbine but such calculations require information for numerous parameters such as flight height, time spent flying per day and agility.
During the X-ROTOR project, we reviewed those parameters for 81 European seabird species and identified vulnerable species to collision and/or disturbance. We also listed numerous species for which disturbance sensitivity and flight height are highly uncertain due to lack of empirical data, potentially biasing our risk assessments. Further, the original design of the X-ROTOR turbine will generate sounds at different frequencies than the usual offshore turbines, potentially reducing/increasing collision and disturbance but studies on seabird uses of acoustic cues are limited.
To fill this gap, our team aimed to collect seabird distribution data as well as flight height and sounds experienced by seabirds on land/ at-sea.
During the two previous summers, when seabirds are accessible because nesting on land, we captured and equipped 133 breeding individuals of 4 seabird species (Atlantic puffin, Manx shearwater, Northern gannet, Lesser Black-backed gull) from 3 small Irish islands (Skellig Michael, Little and Great Saltee). We deployed GPS and microphone as well as accelerometer and temperature-depth recorder to accurately describe their at-sea behaviour. Each deployment weighted less than 3% of the bird body mass (from 400g for Atlantic puffin to 3kg for Northern gannet) in order to limit negative impacts. After few days (between 2 and 10) during which birds did at-least one foraging trip at sea, we recaptured most of the equipped individuals to retrieve loggers and download the precious data. Recapture is often playing the waiting game at seabird colonies as birds can spend more than 6 hours at sea before coming back to the nest only for a few minutes, and patience and luck are both mandatory ! The excellent recapture rates in 2021 have allowed preliminary analysis on species distribution (where are they?) and at-sea behaviour (to do what?). Unfortunately, most onboard microphones deployed in 2021 malfunctioned and avian flu dramatically shortened our fieldwork mission in 2022. We hope to supplement the existing dataset this year if the conditions allow it.