Influence of wind on kittiwake Rissa tridactyla flight and offshore wind turbine collision risk

Kittiwake, by Richard Jackson / BTO

Author(s): Davies, J.G., Boersch-Supan, P.H., Clewley, G.D., Humphreys, E.M., O’Hanlon, N.J., Shamoun-Baranes, J., Thaxter, C.B., Weston, E. & Cook, A.S.C.P.

Published: September 2024  

Journal: Marine Biology Volume: 171

Article No.: 191

Digital Identifier No. (DOI): 10.1007/s00227-024-04508-0

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Climate change presents a major threat to populations of seabirds such as the Kittiwake, a Red-listed species of conservation concern. However, one mitigation approach to climate change – exploiting renewable energy through offshore wind farms – itself poses a potential threat to kittiwakes, partly due to collision risk with turbine blades.

Many new offshore wind farms are planned, but much uncertainty remains in Kittiwake collision risk, which makes decision-making around offshore wind farm development less efficient. Environmental factors like wind influence the mode, height and speed of seabird flight, and therefore the risk of collision with turbines. Therefore, understanding how wind influences turbine collision risk for Kittiwake could help improve collision risk estimates and identify collision mitigation measures.

In this study, 20 Kittiwakes breeding in Aberdeenshire were fitted with GPS telemetry devices in 2021 to estimate the effect of windspeed and direction on behavioural state, proportion of flight at collision risk height, probability of collision when within the rotor-swept zone, and overall collision risk.

Wind had different effects on different components of Kittiwake collision risk with offshore wind turbines. As windspeed increased, Kittiwakes commuted less and rested more. With increasing windspeed, Kittiwakes spent a considerably smaller proportion of their flight time in the rotor-swept zone, but had a slightly higher probability of collision while in it. The overall effect of increasing windspeed on collision risk was negative, although the effect of wind on avoidance rate was not investigated. In general, relationships between windspeed and Kittiwake flight metrics were fairly uncertain, because they depended on wind direction or varied between individuals.

One key conclusion of this study is that windspeed had a negative effect on Kittiwake collision risk. This means that Kittiwake collision risk estimates could be biased if they are based solely on Kittiwake flight data collected in benign conditions. Another key conclusion is that there is considerable uncertainty in the relationship between windspeed and Kittiwake collision risk. This means that incorporating effects of windspeed into collision risk estimates may only slightly increase their precision and accuracy. Similarly, it is known that bat collision fatalities can be reduced by raising the ‘cut-in’ windspeed above which wind turbines generate power, but the uncertainty of the relationship between windspeed and Kittiwake collision risk makes it unclear whether this mitigation tool would be so effective for Kittiwakes.

Abstract

Offshore windfarms are a potential threat to seabirds, partly due to collision risk with turbine blades. Wind influences the mode, height and speed of seabird flight, and therefore the risk of collision with turbines. We investigated how wind influences the flight of black-legged kittiwakes Rissa tridactyla, a gull of conservation concern, in order to incorporate these findings into collision risk estimates and identify mitigation measures. We used GPS telemetry data (23rd June to 10th August 2021) from 20 kittiwakes breeding in Aberdeenshire, UK (57.385°N, 1.868°W) to estimate the effect of wind on behavioural state, proportion of flight at collision risk height, probability of collision within the rotor-swept zone, and overall collision risk. We found that as windspeed increases, kittiwakes commute less and rest more. With increasing windspeed, kittiwakes spend a considerably smaller proportion of their flight time in the rotor-swept zone, but have a slightly higher probability of collision while in it. Uncertainty was high for most relationships between windspeed and kittiwake flight. Although we did not model avoidance rate, we found the overall effect of windspeed on collision risk to be negative. Effects of windspeed on collision risk are largely mediated through effects on commuting flight, and are contingent on wind direction. Collision risk estimates incorporating the effects of windspeed may have greater precision and accuracy, but considerable uncertainty in windspeed-flight parameter relationships remains. Therefore although kittiwake collision risk may be mitigated by raising the windspeed above which wind turbines generate power, the magnitude of this effect is uncertain.

Notes

The authors are very grateful to Grampian Ringing Group for help with tagging and monitoring, to residents of Whinnyfold for hosting the tag base station, and to Willem Bouten for advice regarding the UvA-BiTS tags. UvA-BiTS studies are facilitated by infrastructures for e-Ecology, developed with support of NLeSC and LifeWatch and carried out on the Dutch national e-infrastructure with the support of SURF Cooperative. Funding was provided by Vattenfall as part of their European Offshore Wind Deployment Centre (EOWDC) scientific research programme.

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