GPS tracking is a valuable tool for increasing our understanding of bird behaviour. In this study, researchers used tracking technology to investigate movements of Amber-listed Lesser Black-backed Gulls around offshore wind farms. Their results reveal a detailed picture of both avoidance of and attraction towards turbines in this species, which may be used to inform future collision risk assessments.

Ireland is now on a legally binding path to net-zero emissions no later than 2050, and to a 51% reduction in emissions by the end of this decade. The Act provides the framework for Ireland to meet its international and EU climate commitments and to become a leader in addressing climate change. The UK and Irish government’s pledge includes investments in offshore wind farms around the UK’s coast. Wind turbines can affect seabirds in several ways, from presenting barriers to their commuting or migratory flight paths and altering habitat to collisions with rotor blades. However, they can also attract foraging seabirds by creating reef-like structures for marine fauna, and pylons can provide attractive roosting sites.

The risk of seabird mortality around wind turbines can be calculated using Collision Risk Models, which inform environmental impact assessments for proposed developments. To provide robust outputs, models rely on accurate data relating to birds’ movements, but the impact of attraction to the foraging or roosting opportunities associated with wind farms on bird behaviour is poorly understood.

To increase our understanding, researchers tracked 25 tagged Lesser Black-backed Gulls from a breeding colony in northwest England from 2014 to 2019. They collected data on the gulls’ avoidance and attraction behaviours in response to nearby offshore wind farms on both large and small scales. By comparing the observed flight paths of the gulls with simulated paths, the scientists determined that the behaviour they observed was not only a consequence of chance.

Significant avoidance behaviour occurred 3 to 4 km outside the wind farm, which weakened nearer the area. The majority of birds did not alter flight routes to avoid wind farms but avoided the turbines when flying within them, remaining outside the rotor area or altering their flight height to avoid the blades. This suggests that the energetic costs of safely navigating rotor blades may be outweighed by the foraging and roosting benefits of entering the wind farm.

The results indicate that avoidance behaviours vary across spatial scales, so the boundary of the area selected for investigation when considering the potential effects of an offshore development may influence the overall avoidance rate calculated. Importantly, the study also notes that its results are indicative of Lesser Black-backed Gulls from only one colony, and only during the breeding season. Interactions with wind farms are likely to vary temporally and between colonies and species too. It is vital that Collision Risk Models take this variation into account.

While there is more research needed to develop Collision Risk Models which accurately reflect bird behaviour in the marine environment, the results of this study are a step toward this. Increasing the accuracy of estimates for avoidance and attraction behaviours will increase the confidence we can have in the outputs of Collision Risk Models and the impact assessments they inform.

Full Article: Johnston DT, Thaxter CB, Boersch-Supan PH, Humphreys EM and others (2022) Investigating avoidance and attraction responses in lesser black-backed gulls Larus fuscus to offshore wind farms. Mar Ecol Prog Ser 686:187-200. Read more here

Read more about Ireland’s ambitious climate act signed into law here