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18 October 2023 Avoidance of offshore wind farms by Sandwich Terns increases with turbine density
Rob S.A. van Bemmelen, Jacco J. Leemans, Mark P. Collier, Ros M.W. Green, Robert P. Middelveld, Chris B. Thaxter, Ruben C. Fijn
Author Affiliations +
Abstract

The expanding use of wind farms as a source of renewable energy can impact bird populations due to collisions and other factors. Globally, seabirds are one of the avian taxonomic groups most threatened by anthropogenic disturbance; adequately assessing the potential impact of offshore wind farms (OWFs) is important for developing strategies to avoid or minimize harm to their populations. We estimated avoidance rates of OWFs—the degree to which birds show reduced utilization of OWF areas—by Sandwich Terns (Thalasseus sandvicensis) at 2 breeding colonies in western Europe: Scolt Head (United Kingdom) and De Putten (the Netherlands). The foraging ranges of birds from each colony overlapped with multiple OWFs. We modeled GPS tracking data using integrated step selection functions (iSSFs) to estimate the relative selection of habitats at the scale of time between successive GPS relocations—in our case, 10 min, in which Sandwich Terns traveled ∼2 km on average. Besides the effects of OWFs and the direct surroundings of OWFs, iSSFs considered distance from the colony and habitat characteristics (water depth and sediment grain size) as well as movement characteristics. Macro-avoidance rates, where 1 means complete avoidance, were estimated at 0.54 (95% CI: 0.35, 0.7) for birds originating from Scolt Head and 0.41 (95% CI: 0.21, 0.56) for those from De Putten. Estimates for individual OWFs also indicated avoidance but were associated with considerable uncertainty. Our results were inconclusive with regard to the behavioral response to the areas directly surrounding OWFs (within 1.5 km); estimates suggested indifference and avoidance, and were associated with large uncertainty. Avoidance rate of OWFs significantly increased with turbine density, suggesting that OWF design may help to reduce the impact of OWFs on Sandwich Terns. The partial avoidance of OWFs by Sandwich Terns implies that the species will experience risks of collision and habitat loss due to OWFs constructed within their foraging ranges.

LAY SUMMARY

  • To assess the effect of offshore wind farms (OWFs) on seabirds, we need to know whether birds enter OWF areas or avoid them.

  • We studied the movements of GPS-tracked Sandwich Terns (Thalasseus sandvicensis) from 2 colonies in western Europe, where multiple OWFs are within the distance that the terns usually travel on their daily trips. We calculated how likely they were to venture into the OWF areas, while accounting for how fast and winding they usually fly.

  • Based on the tracked movements, Sandwich Terns reduced their use of the OWF areas by an average of 41% at one colony and 54% at the other, compared to what we expected. They avoided wind farms more when the turbines were closer together.

  • The results can be used to calculate how many Sandwich Terns fly through an OWF, which is important for calculating the number of potential collision victims. Our study indicates that the impact of OWFs on the space use of Sandwich Terns can be reduced by building OWFs outside their regular foraging range and by placing turbines farther apart.

La creciente utilización de parques eólicos como fuente de energía renovable puede afectar a las poblaciones de aves debido a colisiones y otros factores. A nivel mundial, las aves marinas son uno de los grupos taxonómicos de aves más amenazados por los disturbios antropogénicos; evaluar adecuadamente el impacto potencial de las granjas eólicas marinas (GEMs) es importante para desarrollar estrategias que eviten o minimicen el daño a sus poblaciones. Estimamos las tasas de evitación de GEMs—el grado en el que las aves muestran una reducción en la utilización de áreas de GEMs—por parte de Thalasseus sandvicensis en dos colonias de cría en Europa occidental: Scolt Head (Reino Unido) y De Putten (Países Bajos). Los rangos de forrajeo de las aves de cada colonia se superponían con varias GEMs. Modelamos los datos de seguimiento por GPS utilizando funciones de selección de pasos integradas (FSPIs) para estimar la selección relativa de hábitats a la escala de tiempo entre sucesivas reubicaciones de GPS; en nuestro caso, cada 10 minutos, en los cuales los individuos de T. sandvicensis se desplazaron en promedio ∼2 km. Además de los efectos de las GEMs y de sus alrededores directos, las FSPIs consideraron la distancia desde la colonia y las características del hábitat (profundidad del agua y tamaño de los granos de sedimento), así como las características del movimiento. Las tasas de evitación a nivel macro, donde 1 significa una evitación completa, se estimaron en 0.54 (95% IC: 0.35, 0.7) para las aves originarias de Scolt Head y 0.41 (95% IC: 0.21, 0.56) para las de De Putten. Las estimaciones para las GEMs individuales también indicaron evitación, pero estuvieron asociadas con una considerable incertidumbre. Nuestros resultados no fueron concluyentes con respecto a la respuesta conductual a las áreas que rodean directamente a las GEMs (dentro de 1.5 km); las estimaciones sugirieron indiferencia y evitación, y estuvieron asociadas con una gran incertidumbre. La tasa de evitación de las GEMs aumentó significativamente con la densidad de las turbinas, lo que sugiere que el diseño de las GEMs puede ayudar a reducir el impacto de las GEMs en T. sandvicensis. La evitación parcial de las GEMs por parte de T. sandvicensis implica que la especie experimentará riesgos de colisión y pérdida de hábitat debido a las GEMs construidas dentro de sus áreas de forrajeo.

Rob S.A. van Bemmelen, Jacco J. Leemans, Mark P. Collier, Ros M.W. Green, Robert P. Middelveld, Chris B. Thaxter, and Ruben C. Fijn "Avoidance of offshore wind farms by Sandwich Terns increases with turbine density," Ornithological Applications 126(1), 1-10, (18 October 2023). https://doi.org/10.1093/ornithapp/duad055
Received: 31 March 2023; Accepted: 29 September 2023; Published: 18 October 2023
KEYWORDS
aves marinas
funciones de selección de pasos integradas
granjas eólicas marinas
integrated step selection functions
macro-avoidance
macro-evitación
movement
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